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159-409: IFF can only positively identify friendly aircraft or other forces. If an IFF interrogation receives no reply or an invalid reply, the object is not positively identified as foe; friendly forces may not properly reply to IFF for various reasons such as equipment malfunction, and parties in the area not involved in the combat, such as civilian airliners, will not be equipped with IFF. IFF is a tool within

318-457: A regenerative receiver , which fed a small amount of the amplified output back into the input, strongly amplifying even small signals as long as they were of a single frequency (like Morse code, but unlike voice transmissions). They were tuned to the signal from the CH radar (20–30 MHz), amplifying it so strongly that it was broadcast back out the aircraft's antenna. Since the signal was received at

477-515: A 250 kg bomb underneath the fuselage, the later model arriving during the battle. The Bf 109, unlike the Stuka , could fight on equal terms with RAF fighters after releasing its ordnance . At the start of the battle, the twin-engined Messerschmitt Bf 110C long-range Zerstörer ("Destroyer") was also expected to engage in air-to-air combat while escorting the Luftwaffe bomber fleet. Although

636-600: A 75 mm 12-pounder, and even a 105 mm gun. Erhardt also had a 12-pounder, while Vickers Maxim offered a 3-pounder and Schneider a 47 mm. The French balloon gun appeared in 1910, it was an 11-pounder but mounted on a vehicle, with a total uncrewed weight of two tons. However, since balloons were slow moving, sights were simple. But the challenges of faster moving aeroplanes were recognised. By 1913 only France and Germany had developed field guns suitable for engaging balloons and aircraft and addressed issues of military organisation. Britain's Royal Navy would soon introduce

795-538: A base for the successful prosecution of the air and sea war against England". On 29 November, OKW "Directive No. 9 – Instructions For Warfare Against The Economy Of The Enemy" stated that once this coastline had been secured, the Luftwaffe together with the Kriegsmarine (German Navy) was to blockade UK ports with sea mines. They were to attack shipping and warships and make air attacks on shore installations and industrial production. This directive remained in force in

954-645: A full military structure. For example, the UK's Anti-Aircraft Command, commanded by a full British Army general was part of ADGB. At its peak in 1941–42 it comprised three AA corps with 12 AA divisions between them. The use of balloons by the U.S. Army during the American Civil War compelled the Confederates to develop methods of combating them. These included the use of artillery, small arms, and saboteurs. They were unsuccessful, and internal politics led

1113-451: A large traverse that could be easily transported on a wagon. Krupp 75 mm guns were supplied with an optical sighting system that improved their capabilities. The German Army also adapted a revolving cannon that came to be known to Allied fliers as the " flaming onion " from the shells in flight. This gun had five barrels that quickly launched a series of 37 mm artillery shells. As aircraft started to be used against ground targets on

1272-557: A last resort once the British economy had been damaged and the Luftwaffe had full air superiority. On 2 July, OKW requested preliminary plans. In Britain, Churchill described "the great invasion scare" as "serving a very useful purpose" by "keeping every man and woman tuned to a high pitch of readiness". Historian Len Deighton stated that on 10 July Churchill advised the War Cabinet that invasion could be ignored, as it "would be

1431-543: A maritime force against attacks by airborne weapons launched from aircraft, ships, submarines and land-based sites". In some armies the term all-arms air defence (AAAD) is used for air defence by nonspecialist troops. Other terms from the late 20th century include "ground based air defence" (GBAD) with related terms " short range air defense " (SHORAD) and man-portable air-defense system (MANPADS). Anti-aircraft missiles are variously called surface-to-air missiles , ("SAMs") and surface-to-air guided weapons (SAGWs). Examples are

1590-567: A more capable opponent than any it had previously met: a sizeable, highly coordinated, well-supplied, modern air force. The Luftwaffe's Messerschmitt Bf 109E and Bf 110C fought against the RAF's workhorse Hurricane Mk I and the less numerous Spitfire Mk I ; Hurricanes outnumbered Spitfires in RAF Fighter Command by about 2:1 when war broke out. The Bf 109E had a better climb rate and was up to 40 mph faster in level flight than

1749-529: A most hazardous and suicidal operation". On 11 July, Hitler agreed with Raeder that invasion would be a last resort, and the Luftwaffe advised that gaining air superiority would take 14 to 28 days. Hitler met his army chiefs, von Brauchitsch and Halder , at the Berchtesgaden on 13 July where they presented detailed plans on the assumption that the navy would provide safe transport. Von Brauchitsch and Halder were surprised that Hitler took no interest in

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1908-513: A new 3.6-inch gun, in 1918. In 1928 a 3.7-inch (94 mm) gun became the preferred solution, but it took six years to gain funding. Production of the QF 3.7-inch gun began in 1937; this gun was used on mobile carriages with the field army and transportable guns on fixed mountings for static positions. At the same time the Royal Navy adopted a new 4.5-inch (113 mm) gun in a twin turret, which

2067-637: A new field mounting was introduced in 1916. Since most attacks were at night, searchlights were soon used, and acoustic methods of detection and locating were developed. By December 1916 there were 183 AA sections defending Britain (most with the 3-inch), 74 with the BEF in France and 10 in the Middle East. AA gunnery was a difficult business. The problem was of successfully aiming a shell to burst close to its target's future position, with various factors affecting

2226-691: A par with the army, navy, or air force. In the Soviet Union, this was called Voyska PVO , and had both fighter aircraft, separate from the air force, and ground-based systems. This was divided into two arms, PVO Strany, the Strategic Air defence Service responsible for Air Defence of the Homeland, created in 1941 and becoming an independent service in 1954, and PVO SV, Air Defence of the Ground Forces. Subsequently, these became part of

2385-496: A plotting station at sector headquarters, who used triangulation to determine the aircraft's location. Known as " pip-squeak ", the system worked, but was labour-intensive and did not display its information directly to the radar operators. A system that worked directly with the radar was clearly desirable. The first active IFF transponder (transmitter/responder) was the IFF Mark I which was used experimentally in 1939. This used

2544-673: A program for a compatible system known as successor IFF (SIFF). Modes 4 and 5 are designated for use by NATO forces. In World War I , eight submarines were sunk by friendly fire and in World War II nearly twenty were sunk this way. Still, IFF has not been regarded a high concern before the 1990s by the US military as not many other countries possess submarines . IFF methods that are analogous to aircraft IFF have been deemed unfeasible for submarines because they would make submarines easier to detect. Thus, having friendly submarines broadcast

2703-466: A series of separate tuners inside tuned to different radar bands that it stepped through using a motorized switch, while an automatic gain control solved the problem of it sending out too much signal. Mark II was technically complete as the war began, but a lack of sets meant it was not available in quantity and only a small number of RAF aircraft carried it by the time of the Battle of Britain . Pip-squeak

2862-515: A signal that the IFF responds to. There are two key differences, however. One is that the interrogation pulse is followed by a 12-bit code similar to the ones sent back by the Mark 3 transponders. The encoded number changes day-to-day. When the number is received and decoded in the aircraft transponder, a further cryptographic encoding is applied. If the result of that operation matches the value dialled into

3021-461: A signal, or somehow increase the submarine's signature (based on acoustics, magnetic fluctuations etc.), are not considered viable. Instead, submarine IFF is done based on carefully defining areas of operation. Each friendly submarine is assigned a patrol area, where the presence of any other submarine is deemed hostile and open to attack. Further, within these assigned areas, surface ships and aircraft refrain from any anti-submarine warfare (ASW); only

3180-446: A similar proposal; when rebuffed, he told Churchill that interference with German domination would mean war. To Hitler's great annoyance, all his diplomacy failed to stop Britain from declaring war when he invaded Poland. During the fall of France, he repeatedly discussed peace efforts with his generals. When Churchill came to power, there was still wide support for Halifax, who as Foreign Secretary openly argued for peace negotiations in

3339-446: A study (in 1939) on the possibility of an invasion of Britain and concluded that it also required naval superiority. The Luftwaffe said invasion could only be "the final act in an already victorious war." Hitler first discussed the idea of an invasion at a 21 May 1940 meeting with Grand Admiral Erich Raeder, who stressed the difficulties and his own preference for a blockade. OKW Chief of Staff Jodl's 30 June report described invasion as

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3498-643: A surprise to the Jagdwaffe , although the German pilots retained a strong belief that the 109 was the superior fighter. The British fighters were equipped with eight Browning .303 (7.7mm) machine guns while most Bf 109Es had two 20mm cannons supplemented by two 7.92mm machine guns. The 20mm cannons were much more effective than the .303; during the Battle it was not unknown for damaged German bombers to limp home with up to two hundred .303 hits. At some altitudes,

3657-659: A waste of strategic effort. The defeat of France in June 1940 introduced the prospect for the first time of independent air action against Britain. A July Fliegercorps I paper asserted that Germany was by definition an air power: "Its chief weapon against England is the Air Force, then the Navy, followed by the landing forces and the Army." In 1940, the Luftwaffe would undertake a " strategic offensive ... on its own and independent of

3816-433: A way for ground controllers to determine whether an aircraft had the right code or not but it did not include a way for the transponder to reject signals from other sources. British military scientists found a way of exploiting this by building their own IFF transmitter called Perfectos , which were designed to trigger a response from any FuG 25a system in the vicinity. When an FuG 25a responded on its 168 MHz frequency,

3975-407: Is a more complex problem and, especially in the 1950s, added significantly to the cost of the radar system. By placing this function on the IFF, the same information could be returned for little additional cost, essentially that of adding a digitizer to the aircraft's altimeter . Modern interrogators generally send out a series of challenges on Mode 3/A and then Mode C, allowing the system to combine

4134-591: Is also defeated, the fundamental conditions for a successful war against England will have been secured. England can then be blockaded from Western France at close quarters by the Air Force, while the Navy with its submarines extend the range of the blockade." When war commenced, Hitler and the OKW ( Oberkommando der Wehrmacht or "High Command of the Armed Forces") issued a series of directives ordering, planning and stating strategic objectives. "Directive No. 1 for

4293-483: Is assisted but not governed by identification friend or foe (IFF) electronic devices originally introduced during the Second World War . While these rules originate at the highest authority, different rules can apply to different types of air defence covering the same area at the same time. AAAD usually operates under the tightest rules. NATO calls these rules "weapon control orders" (WCO), they are: Until

4452-639: Is deployed in several ways: Air defence has included other elements, although after the Second World War most fell into disuse: Passive air defence is defined by NATO as "Passive measures taken for the physical defence and protection of personnel, essential installations and equipment in order to minimise the effectiveness of air and/or missile attack". It remains a vital activity by ground forces and includes camouflage and concealment to avoid detection by reconnaissance and attacking aircraft. Measures such as camouflaging important buildings were common in

4611-541: Is derived from the This was their finest hour speech delivered by Winston Churchill in the House of Commons on 18 June, more than three weeks prior to the generally accepted date for the start of the battle: ... What General Weygand called the Battle of France is over. I expect that the battle of Britain is about to begin. Upon this battle depends the survival of Christian civilization. Upon it depends our own British life and

4770-454: Is operated by specialists, batteries may have several dozen teams deploying separately in small sections; self-propelled air defence guns may deploy in pairs. Batteries are usually grouped into battalions or equivalent. In the field army, a light gun or SHORAD battalion is often assigned to a manoeuvre division. Heavier guns and long-range missiles may be in air-defence brigades and come under corps or higher command. Homeland air defence may have

4929-529: Is reserved to me. Attacks on the English homeland are to be prepared, bearing in mind that inconclusive results with insufficient forces are to be avoided in all circumstances. Both France and the UK declared war on Germany; on 9 October, Hitler's "Directive No. 6" planned the offensive to defeat these allies and "win as much territory as possible in the Netherlands, Belgium, and northern France to serve as

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5088-462: Is the counter to aerial warfare and includes "all measures designed to nullify or reduce the effectiveness of hostile air action". It encompasses surface-based, subsurface ( submarine-launched ), and air-based weapon systems, in addition to associated sensor systems, command and control arrangements, and passive measures (e.g. barrage balloons ). It may be used to protect naval , ground , and air forces in any location. However, for most countries,

5247-414: Is to detect hostile aircraft and destroy them. The critical issue is to hit a target moving in three-dimensional space; an attack must not only match these three coordinates, but must do so at the time the target is at that position. This means that projectiles either have to be guided to hit the target, or aimed at the predicted position of the target at the time the projectile reaches it, taking into account

5406-586: Is usually accomplished via the combined use of systems optimized for either short-, medium-, or long-range air defence. In some countries, such as Britain and Germany during the Second World War , the Soviet Union , and modern NATO and the United States, ground-based air defence and air defence aircraft have been under integrated command and control. However, while overall air defence may be for homeland defence (including military facilities), forces in

5565-425: The 13-pr QF 9 cwt and these proved much more satisfactory. However, in general, these ad hoc solutions proved largely useless. With little experience in the role, no means of measuring target, range, height or speed the difficulty of observing their shell bursts relative to the target gunners proved unable to get their fuse setting correct and most rounds burst well below their targets. The exception to this rule

5724-526: The Luftwaffe was formally announced, with Walther Wever as Chief of Staff. The 1935 Luftwaffe doctrine for "Conduct of Air War" ( Luftkriegführung ) set air power within the overall military strategy, with critical tasks of attaining (local and temporary) air superiority and providing battlefield support for army and naval forces. Strategic bombing of industries and transport could be decisive longer-term options, dependent on opportunity or preparations by

5883-463: The QF 3-inch and QF 4-inch AA guns and also had Vickers 1-pounder quick firing "pom-poms" that could be used in various mountings. The first US anti-aircraft cannon was a 1-pounder concept design by Admiral Twining in 1911 to meet the perceived threat of airships, that eventually was used as the basis for the US Navy's first operational anti-aircraft cannon: the 3-inch/23 caliber gun . On

6042-479: The RAF had considered the problem of IFF. Robert Watson-Watt had filed patents on such systems in 1935 and 1936. By 1938, researchers at Bawdsey Manor began experiments with "reflectors" consisting of dipole antennas tuned to resonate to the primary frequency of the CH radars. When a pulse from the CH transmitter hit the aircraft, the antennas would resonate for a short time, increasing the amount of energy returned to

6201-671: The RIM-66 Standard , Raytheon Standard Missile 6 , or the MBDA Aster missile. Non-English terms for air defence include the German Flak or FlaK ( Fliegerabwehrkanone , 'aircraft defence cannon', also cited as Flugabwehrkanone ), whence English flak , and the Russian term Protivovozdushnaya oborona ( Cyrillic : Противовозду́шная оборо́на), a literal translation of 'anti-air defence', abbreviated as PVO. In Russian,

6360-675: The Royal Naval Volunteer Reserve (RNVR) was manning AA guns and searchlights assembled from various sources at some nine ports. The Royal Garrison Artillery (RGA) was given responsibility for AA defence in the field, using motorised two-gun sections. The first were formally formed in November 1914. Initially they used QF 1-pounder "pom-pom"s (37 mm versions of the Maxim Gun ). All armies soon deployed AA guns often based on their smaller field pieces, notably

6519-633: The United States Air Force 's operating bases in the UK. All ground-based air defence was removed from Royal Air Force (RAF) jurisdiction in 2004 . The British Army's Anti-Aircraft Command was disbanded in March 1955, but during the 1960s and 1970s the RAF's Fighter Command operated long-range air-defence missiles to protect key areas in the UK. During World War II, the Royal Marines also provided air defence units; formally part of

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6678-649: The 1950s, guns firing ballistic munitions were the standard weapon; guided missiles then became dominant, except at the very shortest ranges. However, the type of shell or warhead and its fuzing and, with missiles, the guidance arrangement were and are varied. Targets are not always easy to destroy; nonetheless, damaged aircraft may be forced to abort their mission and, even if they manage to return and land in friendly territory, may be out of action for days or permanently. Ignoring small arms and smaller machine-guns, ground-based air defence guns have varied in calibre from 20 mm to at least 152 mm. Ground-based air defence

6837-471: The 30th of September, 1915, troops of the Serbian Army observed three enemy aircraft approaching Kragujevac . Soldiers fired at them with shotguns and machine-guns but failed to prevent them from dropping 45 bombs over the city, hitting military installations, the railway station and many other, mostly civilian, targets in the city. During the bombing raid, private Radoje Ljutovac fired his cannon at

6996-420: The 8.8 cm FlaK 18 in 1933, the 36 and 37 models followed with various improvements, but ballistic performance was unchanged. In the late 1930s the 10.5 cm FlaK 38 appeared, soon followed by the 39; this was designed primarily for static sites but had a mobile mounting, and the unit had 220 V 24 kW generators. In 1938 design started on the 12.8 cm FlaK . Britain had successfully tested

7155-487: The AA systems are called zenitnye (i.e., 'pointing to zenith ') systems. In French, air defence is called Défense contre les aéronefs (DCA) , aéronef meaning 'aircraft'. The maximum distance at which a gun or missile can engage an aircraft is an important figure. However, many different definitions are used and unless the same definition is used, performance of different guns or missiles cannot be compared. For AA guns only

7314-585: The Battle period he sought neutrality or a peace treaty with Britain. In a secret conference on 23 May 1939, Hitler set out his rather contradictory strategy that an attack on Poland was essential and "will only be successful if the Western Powers keep out of it. If this is impossible, then it will be better to attack in the West and to settle Poland at the same time" with a surprise attack. "If Holland and Belgium are successfully occupied and held, and if France

7473-595: The Bf 109 could outclimb the British fighter. It could also engage in vertical-plane negative- g manoeuvres without the engine cutting out because its DB 601 engine used fuel injection ; this allowed the 109 to dive away from attackers more readily than the carburettor -equipped Merlin. On the other hand, the Bf 109E had a much larger turning circle than its two foes. In general, though, as Alfred Price noted in The Spitfire Story : ... the differences between

7632-538: The British Foreign Secretary , Lord Halifax , and certain elements of the British public favoured a negotiated peace with an ascendant Germany, Churchill and a majority of his Cabinet refused to consider an armistice. Instead, Churchill used his skilful rhetoric to harden public opinion against capitulation and prepare the British for a long war. The Battle of Britain has the unusual distinction that it gained its name before being fought. The name

7791-492: The British Isles increased in 1915 and the AA efforts were deemed somewhat ineffective, so a Royal Navy gunnery expert, Admiral Sir Percy Scott , was appointed to make improvements, particularly an integrated AA defence for London. The air defences were expanded with more RNVR AA guns, 75 mm and 3-inch, the pom-poms being ineffective. The naval 3-inch was also adopted by the army, the QF 3-inch 20 cwt (76 mm),

7950-491: The British adopted a new instrument developed by Vickers. It was a mechanical analogue computer - the Predictor AA No 1. Given the target height, its operators tracked the target and the predictor produced bearing, quadrant elevation and fuse setting. These were passed electrically to the guns, where they were displayed on repeater dials to the layers who "matched pointers" (target data and the gun's actual data) to lay

8109-591: The British designs. This technique is now known as a cross-band transponder . When the Mark II was revealed in 1941 during the Tizard Mission , it was decided to use it and take the time to further improve their experimental system. The result was what became IFF Mark IV. The main difference between this and earlier models is that it worked on higher frequencies, around 600 MHz, which allowed much smaller antennas. However, this also turned out to be close to

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8268-527: The British trade". Instead of the Wehrmacht attacking the French, the Luftwaffe with naval assistance was to block imports to Britain and attack seaports. "Should the enemy resort to terror measures – for example, to attack our towns in western Germany" they could retaliate by bombing industrial centres and London. Parts of this appeared on 29 November in "Directive No. 9" as future actions once

8427-563: The CH receiver. The antenna was connected to a motorized switch that periodically shorted it out, preventing it from producing a signal. This caused the return on the CH set to periodically lengthen and shorten as the antenna was turned on and off. In practice, the system was found to be too unreliable to use; the return was highly dependent on the direction the aircraft was moving relative to the CH station, and often returned little or no additional signal. It had been suspected this system would be of little use in practice. When that turned out to be

8586-551: The Channel. In September, RAF Bomber Command night raids disrupted the German preparation of converted barges, and the Luftwaffe's failure to overwhelm the RAF forced Hitler to postpone and eventually cancel Operation Sea Lion. The Luftwaffe proved unable to sustain daylight raids, but their continued night-bombing operations on Britain became known as the Blitz. Germany's failure to destroy Britain's air defences and force it out of

8745-632: The Conduct of the War", dated 31 August 1939, instructed the invasion of Poland on 1 September as planned . Potentially, Luftwaffe "operations against England" were to: dislocate English imports, the armaments industry, and the transport of troops to France. Any favourable opportunity of an effective attack on concentrated units of the English Navy, particularly on battleships or aircraft carriers, will be exploited. The decision regarding attacks on London

8904-419: The French 75 mm and Russian 76.2 mm, typically simply propped up on some sort of embankment to get the muzzle pointed skyward. The British Army adopted the 13-pounder quickly producing new mountings suitable for AA use, the 13-pdr QF 6 cwt Mk III was issued in 1915. It remained in service throughout the war but 18-pdr guns were lined down to take the 13-pdr shell with a larger cartridge producing

9063-401: The French surrender on 22 June 1940, Hitler mainly focused his energies on the possibility of invading the Soviet Union . He believed that the British, defeated on the continent and without European allies, would quickly come to terms. The Germans were so convinced of an imminent armistice that they began constructing street decorations for the homecoming parades of victorious troops. Although

9222-563: The German Flugzeugabwehrkanone ), "ack-ack" (from the spelling alphabet used by the British for voice transmission of "AA"); and "archie" (a World War I British term probably coined by Amyas Borton , and believed to derive via the Royal Flying Corps , from the music-hall comedian George Robey 's line "Archibald, certainly not!" ). NATO defines anti-aircraft warfare (AAW) as "measures taken to defend

9381-412: The IFF in the aircraft, the transponder replies with a Mode 3 response as before. If the values do not match, it does not respond. This solves the problem of the aircraft transponder replying to false interrogations, but does not completely solve the problem of locating the aircraft through triangulation. To solve this problem, a delay is added to the response signal that varies based on the code sent from

9540-616: The Low Countries in the Battle of France , leaving Britain to face the threat of invasion by sea. The German high command recognised the difficulties of a seaborne attack while the Royal Navy controlled the English Channel and the North Sea . On 16 July, Hitler ordered the preparation of Operation Sea Lion as a potential amphibious and airborne assault on Britain, to follow once the Luftwaffe had air superiority over

9699-403: The Luftwaffe lacked the means to do much damage to Britain's war economy beyond laying naval mines . Joseph Schmid , in charge of Luftwaffe intelligence, presented a report on 22 November 1939, stating that, "Of all Germany's possible enemies, Britain is the most dangerous." This "Proposal for the Conduct of Air Warfare" argued for a counter to the British blockade and said "Key is to paralyse

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9858-604: The Luftwaffe mainly targeting coastal-shipping convoys, as well as ports and shipping centres such as Portsmouth . On 1 August, the Luftwaffe was directed to achieve air superiority over the RAF, with the aim of incapacitating RAF Fighter Command ; 12 days later , it shifted the attacks to RAF airfields and infrastructure . As the battle progressed, the Luftwaffe also targeted factories involved in aircraft production and strategic infrastructure. Eventually, it employed terror bombing on areas of political significance and on civilians. The Germans had rapidly overwhelmed France and

10017-850: The Minister in charge of Defence Coordination, Sir Thomas Inskip , sided with Dowding that "The role of our air force is not an early knock-out blow" but rather was "to prevent the Germans from knocking us out" and fighter squadrons were just as necessary as bomber squadrons. The Spanish Civil War (1936–1939) gave the Luftwaffe Condor Legion the opportunity to test air fighting tactics with their new aeroplanes. Wolfram von Richthofen became an exponent of air power providing ground support to other services. The difficulty of accurately hitting targets prompted Ernst Udet to require that all new bombers had to be dive bombers , and led to

10176-463: The Mode S data. The IFF of World War II and Soviet military systems (1946 to 1991) used coded radar signals (called cross-band interrogation, or CBI) to automatically trigger the aircraft's transponder in an aircraft illuminated by the radar. Radar-based aircraft identification is also called secondary surveillance radar in both military and civil usage, with primary radar bouncing an RF pulse off of

10335-522: The OKW reviewed the potential for an air- and seaborne invasion of Britain: the Kriegsmarine was faced with the threat the Royal Navy's larger Home Fleet posed to a crossing of the English Channel , and together with the German Army viewed control of airspace as a necessary precondition. The German navy thought air superiority alone was insufficient; the German naval staff had already produced

10494-414: The RAF. But the introduction of radars based on the microwave -frequency cavity magnetron rendered this obsolete; there was simply no way to make a responder operating in this band using contemporary electronics. In 1940, English engineer Freddie Williams had suggested using a single separate frequency for all IFF signals, but at the time there seemed no pressing need to change the existing system. With

10653-477: The Rotol (constant speed propeller) equipped Hurricane Mk I, depending on altitude. The speed and climb disparity with the original non-Rotol Hurricane was even greater. By mid-1940, all RAF Spitfire and Hurricane fighter squadrons converted to 100 octane aviation fuel, which allowed their Merlin engines to generate significantly more power and an approximately 30 mph increase in speed at low altitudes through

10812-473: The Second World War. During the Cold War the runways and taxiways of some airfields were painted green. While navies are usually responsible for their own air defence—at least for ships at sea—organisational arrangements for land-based air defence vary between nations and over time. The most extreme case was the Soviet Union and this model may still be followed in some countries: it was a separate service, on

10971-474: The Soviet Union. Erhard Milch organised rapid expansion, and following the 1933 Nazi seizure of power , his subordinate Robert Knauss formulated a deterrence theory incorporating Douhet's ideas and Tirpitz's "risk theory" . This proposed a fleet of heavy bombers to deter a preventive attack by France and Poland before Germany could fully rearm. A 1933–34 war game indicated a need for fighters and anti-aircraft protection as well as bombers. On 1 March 1935,

11130-619: The Spitfire and the Me 109 in performance and handling were only marginal, and in a combat they were almost always surmounted by tactical considerations of which side had seen the other first, which had the advantage of sun, altitude, numbers, pilot ability, tactical situation, tactical co-ordination, amount of fuel remaining, etc. The Bf 109E was also used as a Jabo ( jagdbomber , fighter-bomber ) – the E-4/B and E-7 models could carry

11289-621: The United States Army's Balloon Corps to be disbanded mid-war. The Confederates experimented with balloons as well. Turks carried out the first ever anti-airplane operation in history during the Italo-Turkish war . Although lacking anti-aircraft weapons, they were the first to shoot down an airplane by rifle fire. The first aircraft to crash in a war was the one of Lieutenant Piero Manzini, shot down on August 25, 1912. The earliest known use of weapons specifically made for

11448-468: The ability to transmit a coded ' Mayday ' response. The IFF sets were designed and built by Ferranti in Manchester to Williams' specifications. Equivalent sets were manufactured in the US, initially as copies of British sets, so that allied aircraft would be identified upon interrogation by each other's radar. IFF sets were obviously highly classified. Thus, many of them were wired with explosives in

11607-481: The abyss of a new Dark Age made more sinister, and perhaps more protracted, by the lights of a perverted science. Let us therefore brace ourselves to our duties, and so bear ourselves that, if the British Empire and its Commonwealth last for a thousand years, men will still say, "This was their finest hour". From the outset of his rise to power, Adolf Hitler expressed admiration for Britain, and throughout

11766-669: The air force and ground forces respectively. At the other extreme, the United States Army has an Air Defense Artillery Branch that provides ground-based air defence for both homeland and the army in the field; however, it is operationally under the Joint Force Air Component Commander . Many other nations also deploy an air-defence branch in the army. Some, such as Japan or Israel, choose to integrate their ground based air defence systems into their air force. In Britain and some other armies,

11925-656: The aircraft to determine position. George Charrier, working for RCA , filed for a patent for such an IFF device in 1941. It required the operator to perform several adjustments to the radar receiver to suppress the image of the natural echo on the radar receiver, so that visual examination of the IFF signal would be possible. By 1943, Donald Barchok filed a patent for a radar system using the abbreviation IFF in his text with only parenthetic explanation, indicating that this acronym had become an accepted term. In 1945, Emile Labin and Edwin Turner filed patents for radar IFF systems where

12084-413: The altitude at which a gun could deliver a series of shells against a moving target; this could be constrained by maximum fuse running time as well as the gun's capability. By the late 1930s the British definition was "that height at which a directly approaching target at 400 mph [640 km/h] can be engaged for 20 seconds before the gun reaches 70 degrees elevation". The essence of air defence

12243-562: The anti-aircraft role occurred during the Franco-Prussian War of 1870. After the disaster at Sedan , Paris was besieged and French troops outside the city started an attempt at communication via balloon . Gustav Krupp mounted a modified 1-pounder (37 mm) gun – the Ballonabwehrkanone (Balloon defence cannon) or BaK — on top of a horse-drawn carriage for the purpose of shooting down these balloons. By

12402-847: The army adopted in simplified single-gun mountings for static positions, mostly around ports where naval ammunition was available. The performance of the new guns was limited by their standard fuse No 199, with a 30-second running time, although a new mechanical time fuse giving 43 seconds was nearing readiness. In 1939 a machine fuse setter was introduced to eliminate manual fuse setting. Battle of Britain Asia-Pacific Mediterranean and Middle East Other campaigns Coups Luxembourg The Netherlands Belgium France Britain 1941–1943 1944–1945 Germany Strategic campaigns The Battle of Britain ( German : Luftschlacht um England , lit.   'air battle for England')

12561-433: The army and navy. It could be used to overcome a stalemate, or used when only destruction of the enemy's economy would be conclusive. The list excluded bombing civilians to destroy homes or undermine morale, as that was considered a waste of strategic effort, but the doctrine allowed revenge attacks if German civilians were bombed. A revised edition was issued in 1940, and the continuing central principle of Luftwaffe doctrine

12720-407: The ascending part of the trajectory can be usefully used. One term is "ceiling", the maximum ceiling being the height a projectile would reach if fired vertically, not practically useful in itself as few AA guns are able to fire vertically, and the maximum fuse duration may be too short, but potentially useful as a standard to compare different weapons. The British adopted "effective ceiling", meaning

12879-457: The battlefield, the AA guns could not be traversed quickly enough at close targets and, being relatively few, were not always in the right place (and were often unpopular with other troops), so changed positions frequently. Soon the forces were adding various machine-gun based weapons mounted on poles. These short-range weapons proved more deadly, and the " Red Baron " is believed to have been shot down by an anti-aircraft Vickers machine gun . When

13038-500: The broader military action of combat identification (CID), the characterization of objects detected in the field of combat sufficiently accurately to support operational decisions. The broadest characterization is that of friend, enemy, neutral, or unknown. CID not only can reduce friendly fire incidents, but also contributes to overall tactical decision-making. With the successful deployment of radar systems for air defence during World War II , combatants were immediately confronted with

13197-445: The case, the RAF turned to an entirely different system that was also being planned. This consisted of a set of tracking stations using HF/DF radio direction finders . Their aircraft radios were modified to send out a 1 kHz tone for 14 seconds every minute, allowing the stations ample time to measure the aircraft's bearing. Several such stations were assigned to each "sector" of the air defence system, and sent their measurements to

13356-400: The civilian air transport system, and it was decided to use slightly modified Mark X sets for these aircraft as well. These sets included a new military Mode 3 which was essentially identical to Mode 2, returning a four-digit code, but used a different interrogation pulse, allowing the aircraft to identify if the query was from a military or civilian radar. For civilian aircraft, this same system

13515-509: The coast had been conquered. On 24 May 1940 "Directive No. 13" authorised attacks on the blockade targets, as well as retaliation for RAF bombing of industrial targets in the Ruhr. After the defeat of France, the OKW felt they had won the war, and some more pressure would persuade Britain to give in. On 30 June, the OKW Chief of Staff Alfred Jodl issued his paper setting out options: the first

13674-408: The competition for a share of limited defence budgets. Demobilisation meant that most AA guns were taken out of service, leaving only the most modern. However, there were lessons to be learned. In particular the British, who had had AA guns in most theatres in action in daylight and used them against night attacks at home. Furthermore, they had also formed an Anti-Aircraft Experimental Section during

13833-402: The conduct of air and sea warfare against England" issued on 1 August attempted to keep all the options open. The Luftwaffe's Adlertag campaign was to start around 5 August, subject to weather, with the aim of gaining air superiority over southern England as a necessary precondition of invasion, to give credibility to the threat and give Hitler the option of ordering the invasion. The intention

13992-439: The continent, and on 30 June the OKW Chief of Staff, Alfred Jodl , issued his review of options to increase pressure on Britain to agree to a negotiated peace. The first priority was to eliminate the RAF and gain air supremacy. Intensified air attacks against shipping and the economy could affect food supplies and civilian morale in the long term. Reprisal attacks of terror bombing had the potential to cause quicker capitulation, but

14151-536: The continuing influence of the 1935 "Conduct of the Air War" doctrine, the main focus of the Luftwaffe command (including Göring) was in concentrating attacks to destroy enemy armed forces on the battlefield, and "blitzkrieg" close air support of the army succeeded brilliantly. They reserved strategic bombing for a stalemate situation or revenge attacks, but doubted if this could be decisive on its own and regarded bombing civilians to destroy homes or undermine morale as

14310-682: The defending armies in Norway in early 1940 created a significant political crisis in Britain. In early May 1940, the Norway Debate questioned the fitness for office of the British Prime Minister Neville Chamberlain . On 10 May, the same day Winston Churchill became British Prime Minister, the Germans initiated the Battle of France with an aggressive invasion of French territory. RAF Fighter Command

14469-551: The development of the Knickebein system for night time navigation. Priority was given to producing large numbers of smaller aeroplanes, and plans for a long-range, four-engined strategic bomber were cancelled. The early stages of the Second World War saw successful German invasions on the continent, aided decisively by the air power of the Luftwaffe, which was able to establish tactical air superiority with great effectiveness. The speed with which German forces defeated most of

14628-504: The difficulty of distinguishing friendly aircraft from hostile ones; by that time, aircraft were flown at high speed and altitude, making visual identification impossible, and the targets showed up as featureless blips on the radar screen. This led to incidents such as the Battle of Barking Creek , over Britain, and the air attack on the fortress of Koepenick over Germany. Already before the deployment of their Chain Home radar system (CH),

14787-678: The early 20th century balloon, or airship, guns, for land and naval use were attracting attention. Various types of ammunition were proposed, high explosive, incendiary, bullet-chains, rod bullets and shrapnel. The need for some form of tracer or smoke trail was articulated. Fuzing options were also examined, both impact and time types. Mountings were generally pedestal type but could be on field platforms. Trials were underway in most countries in Europe but only Krupp, Erhardt, Vickers Maxim, and Schneider had published any information by 1910. Krupp's designs included adaptations of their 65 mm 9-pounder,

14946-536: The effect on morale was uncertain. On the same day, the Luftwaffe Commander-in-Chief, Hermann Göring issued his operational directive: to destroy the RAF, thus protecting German industry, and also to block overseas supplies to Britain. The German Supreme Command argued over the practicality of these options. In "Directive No. 16 – On preparations for a landing operation against England" on 16 July, Hitler required readiness by mid-August for

15105-490: The enemy aircraft and successfully shot one down. It crashed in the city and both pilots died from their injuries. The cannon Ljutovac used was not designed as an anti-aircraft gun; it was a slightly modified Turkish cannon captured during the First Balkan War in 1912. This was the first occasion in military history that a military aircraft was shot down with ground-to-air artillery fire. The British recognised

15264-415: The event the aircrew bailed out or crash landed. Jerry Proc reports: Alongside the switch to turn on the unit was the IFF destruct switch to prevent its capture by the enemy. Many a pilot chose the wrong switch and blew up his IFF unit. The thud of a contained explosion and the acrid smell of burning insulation in the cockpit did not deter many pilots from destroying IFF units time and time again. Eventually,

15423-654: The field, wherever they are, provide their own defences against airborne threats. Until the 1950s, guns firing ballistic munitions ranging from 7.62 mm (.30 in) to 152.4 mm (6 in) were the standard weapons; guided missiles then became dominant, except at the very shortest ranges (as with close-in weapon systems , which typically use rotary autocannons or, in very modern systems, surface-to-air adaptations of short-range air-to-air missiles , often combined in one system with rotary cannons). It may also be called counter-air , anti-air , AA , flak , layered air defence or air defence forces . The term air defence

15582-621: The first independent strategic bombing campaign. Hitler's 1925 book Mein Kampf mostly set out his hatreds: he only admired ordinary German World War I soldiers and Britain, which he saw as an ally against communism. In 1935 Hermann Göring welcomed news that Britain, as a potential ally, was rearming. In 1936 he promised assistance to defend the British Empire, asking only a free hand in Eastern Europe, and repeated this to Lord Halifax in 1937. That year, von Ribbentrop met Churchill with

15741-475: The first phase of the Battle of Britain. It was reinforced on 24 May during the Battle of France by "Directive No. 13", which authorised the Luftwaffe "to attack the English homeland in the fullest manner, as soon as sufficient forces are available. This attack will be opened by an annihilating reprisal for English attacks on the Ruhr Basin." By the end of June 1940, Germany had defeated Britain's allies on

15900-596: The frequencies used by the German Würzburg radar and there were concerns that it would be triggered by that radar and the transponder responses would be picked on its radar display. This would immediately reveal the IFF's operational frequencies. This led to a US–British effort to make a further improved model, the Mark V, also known as the United Nations Beacon or UNB. This moved to still higher frequencies around 1 GHz but operational testing

16059-584: The ground-based air defence of the British Army's Anti-Aircraft Command , although field-deployed air defence relied on less sophisticated arrangements. NATO later called these arrangements an "air defence ground environment", defined as "the network of ground radar sites and command and control centres within a specific theatre of operations which are used for the tactical control of air defence operations". Rules of engagement are critical to prevent air defences engaging friendly or neutral aircraft. Their use

16218-484: The guns. This system of repeater electrical dials built on the arrangements introduced by British coast artillery in the 1880s, and coast artillery was the background of many AA officers. Similar systems were adopted in other countries and for example the later Sperry M3A3 in the US, was also used by Britain as the Predictor AA No 2. Height finders were also increasing in size; in Britain, the seven-foot optical base World War I Barr & Stroud UB 2 stereoscopic rangefinder

16377-505: The identity of the aircraft with its altitude and location from the radar. The current IFF system is the Mark XII. This works on the same frequencies as Mark X, and supports all of its military and civilian modes. It had long been considered a problem that the IFF responses could be triggered by any properly formed interrogation, and those signals were simply two short pulses of a single frequency. This allowed enemy transmitters to trigger

16536-427: The interrogator. When received by an enemy that does not see the interrogation pulse, which is generally the case as they are often below the radar horizon , this causes a random displacement of the return signal with every pulse. Locating the aircraft within the set of returns is a difficult process. During the 1980s, a new civilian mode, Mode S, was added that allowed greatly increased amounts of data to be encoded in

16695-748: The introduction of the magnetron, work on this concept began at the Telecommunications Research Establishment as the IFF Mark III . This was to become the standard for the Western Allies for most of the war. Mark III transponders were designed to respond to specific 'interrogators', rather than replying directly to received radar signals. These interrogators worked on a limited selection of frequencies, no matter what radar they were paired with. The system also allowed limited communication to be made, including

16854-473: The invasion plans, unlike his usual attitude toward military operations, but on 16 July he issued Directive No. 16, ordering preparations for Operation Sea Lion. The navy insisted on a narrow beachhead and an extended period for landing troops; the army rejected these plans: the Luftwaffe could begin an air attack in August. Hitler held a meeting of his army and navy chiefs on 31 July. The navy said 22 September

17013-436: The late 1930s for development work on sound-locating acoustic devices to be generally halted, although equipment was retained. Furthermore, in Britain the volunteer Observer Corps formed in 1925 provided a network of observation posts to report hostile aircraft flying over Britain. Initially radar was used for airspace surveillance to detect approaching hostile aircraft. However, the German Würzburg radar put into use in 1940

17172-453: The long continuity of our institutions and our Empire . The whole fury and might of the enemy must very soon be turned on us. Hitler knows that he will have to break us in this island or lose the war. If we can stand up to him, all Europe may be free and the life of the world may move forward into broad, sunlit uplands. But if we fail, then the whole world, including the United States, including all that we have known and cared for, will sink into

17331-601: The main effort has tended to be homeland defence . Missile defence is an extension of air defence, as are initiatives to adapt air defence to the task of intercepting any projectile in flight. Most modern anti-aircraft (AA) weapons systems are optimized for short-, medium-, or long-range air defence, although some systems may incorporate multiple weapons (such as both autocannons and surface-to-air missiles ). ‘Layered air defence’ usually refers to multiple ‘tiers’ of air defence systems which, when combined, an airborne threat must penetrate in order to reach its target; This defence

17490-528: The merger of the British army and navy air services into the Royal Air Force (RAF). Its first Chief of the Air Staff , Hugh Trenchard , was among the military strategists in the 1920s, like Giulio Douhet , who saw air warfare as a new way to overcome the bloody stalemate of trench warfare . Interception was expected to be nearly impossible, with fighter planes no faster than bombers. Their slogan

17649-513: The mobile naval base defence organisation, they were handled as an integral part of the army-commanded ground based air defences. The basic air defence unit is typically a battery with 2 to 12 guns or missile launchers and fire control elements. These batteries, particularly with guns, usually deploy in a small area, although batteries may be split; this is usual for some missile systems. SHORAD missile batteries often deploy across an area with individual launchers several kilometres apart. When MANPADS

17808-494: The need for anti-aircraft capability a few weeks before World War I broke out; on 8 July 1914, the New York Times reported that the British government had decided to "dot the coasts of the British Isles with a series of towers, each armed with two quick-firing guns of special design," while "a complete circle of towers" was to be built around "naval installations" and "at other especially vulnerable points". By December 1914

17967-521: The other services", according to an April 1944 German account of their military mission. Göring was convinced that strategic bombing could win objectives that were beyond the army and navy, and gain political advantages in the Third Reich for the Luftwaffe and himself. He expected air warfare to decisively force Britain to negotiate, as all in the OKW hoped, and the Luftwaffe took little interest in planning to support an invasion. The Luftwaffe faced

18126-452: The outgoing radar signal and the transponder's reply signal could each be independently programmed with a binary codes by setting arrays of toggle switches; this allowed the IFF code to be varied from day to day or even hour to hour. The United States and other NATO countries started using a system called Mark XII in the late twentieth century; Britain had not until then implemented an IFF system compatible with that standard, but then developed

18285-425: The period of large-scale night attacks known as the Blitz , that lasted from 7 September 1940 to 11 May 1941. German historians do not follow this subdivision and regard the battle as a single campaign lasting from July 1940 to May 1941, including the Blitz. The primary objective of the German forces was to compel Britain to agree to a negotiated peace settlement . In July 1940, the air and sea blockade began, with

18444-412: The possibility of an invasion he called Operation Sea Lion , unless the British agreed to negotiations. The Luftwaffe reported that it would be ready to launch its major attack early in August. The Kriegsmarine Commander-in-Chief, Grand Admiral Erich Raeder , continued to highlight the impracticality of these plans and said sea invasion could not take place before early 1941. Hitler now argued that Britain

18603-465: The resident submarine may target other submarines in its own area. Ships and aircraft may still engage in ASW in areas that have not been assigned to any friendly submarines. Navies also use database of acoustic signatures to attempt to identify the submarine, but acoustic data can be ambiguous and several countries deploy similar classes of submarines. Anti-aircraft warfare Anti-aircraft warfare

18762-522: The response, and using triangulation , an enemy could determine the location of the transponder. The British had already used this technique against the Germans during WWII, and it was used by the USAF against VPAF aircraft during the Vietnam War . Mark XII differs from Mark X through the addition of the new military Mode 4. This works in a fashion similar to Mode 3/A, with the interrogator sending out

18921-401: The return signal to contain up to 12 pulses, representing four octal digits of 3 bits each. Depending on the timing of the interrogation signal, SIF would respond in several ways. Mode 1 indicated the type of aircraft or its mission (cargo or bomber, for instance) while Mode 2 returned a tail code. Mark X began to be introduced in the early 1950s. This was during a period of great expansion of

19080-435: The returned signal. This was used to encode the location of the aircraft from the navigation system. This is a basic part of the traffic collision avoidance system (TCAS), which allows commercial aircraft to know the location of other aircraft in the area and avoid them without the need for ground operators. The basic concepts from Mode S were then militarized as Mode 5, which is simply a cryptographically encoded version of

19239-439: The same time as the original reflection of the CH signal, the result was a lengthened "blip" on the CH display which was easily identifiable. In testing, it was found that the unit would often overpower the radar or produce too little signal to be seen, and at the same time, new radars were being introduced using new frequencies. Instead of putting Mark I into production, a new IFF Mark II was introduced in early 1940. Mark II had

19398-527: The self destruct switch was secured by a thin wire to prevent its accidental use." FuG 25a Erstling (English: Firstborn, Debut) was developed in Germany in 1940. It was tuned to the low- VHF band at 125 MHz used by the Freya radar , and an adaptor was used with the low- UHF -banded 550–580 MHz used by Würzburg . Before a flight, the transceiver was set up with a selected day code of ten bits which

19557-461: The shells' predicted trajectory. This was called deflection gun-laying, where "off-set" angles for range and elevation were set on the gunsight and updated as their target moved. In this method, when the sights were on the target, the barrel was pointed at the target's future position. Range and height of the target determined fuse length. The difficulties increased as aircraft performance improved. The British dealt with range measurement first, when it

19716-461: The signal was received by the antenna system from an AI Mk. IV radar , which originally operated at 212 MHz. By comparing the strength of the signal on different antennas the direction to the target could be determined. Mounted on Mosquitos , the "Perfectos" severely limited German use of the FuG 25a. The United States Naval Research Laboratory had been working on their own IFF system since before

19875-643: The single artillery branch has been responsible for both home and overseas ground-based air defence, although there was divided responsibility with the Royal Navy for air defence of the British Isles in World War I . However, during the Second World War , the RAF Regiment was formed to protect airfields everywhere, and this included light air defences. In the later decades of the Cold War this included

20034-477: The speed and direction of both the target and the projectile. Throughout the 20th century, air defence was one of the fastest-evolving areas of military technology, responding to the evolution of aircraft and exploiting technology such as radar, guided missiles and computing (initially electromechanical analogue computing from the 1930s on, as with equipment described below). Improvements were made to sensors, technical fire control, weapons, and command and control. At

20193-422: The start of the 20th century these were either very primitive or non-existent. Initially sensors were optical and acoustic devices developed during World War I and continued into the 1930s, but were quickly superseded by radar, which in turn was supplemented by optoelectronics in the 1980s. Command and control remained primitive until the late 1930s, when Britain created an integrated system for ADGB that linked

20352-463: The target and having its height. Second, that the target would maintain a steady course, speed and height. This HAA was to engage targets up to 24,000 ft (7.3 km). Mechanical time fuses were required because the speed of powder burning varied with height, so fuse length was not a simple function of time of flight. Automated fire ensured a constant rate of fire that made it easier to predict where each shell should be individually aimed. In 1925

20511-579: The tradition of British diplomacy, to secure British independence without war. On 20 May, Halifax secretly requested a Swedish businessman to make contact with Göring to open negotiations. Shortly afterwards, in the May 1940 War Cabinet Crisis , Halifax argued for negotiations involving the Italians, but this was rejected by Churchill with majority support. An approach made through the Swedish ambassador on 22 June

20670-427: The use of an Emergency Boost Override . In September 1940, the more powerful Mk IIa series 1 Hurricanes started entering service in small numbers. This version was capable of a maximum speed of 342 mph (550 km/h), some 20 mph more than the original (non-Rotol) Mk I, though it was still 15 to 20 mph slower than a Bf 109 (depending on altitude). The performance of the Spitfire over Dunkirk came as

20829-409: The war and accumulated large amounts of data that was subjected to extensive analysis. As a result, they published the two-volume Textbook of Anti-Aircraft Gunnery in 1924–1925. It included five key recommendations for HAA equipment: Two assumptions underpinned the British approach to HAA fire; first, aimed fire was the primary method and this was enabled by predicting gun data from visually tracking

20988-437: The war ended, it was clear that the increasing capabilities of aircraft would require better means of acquiring targets and aiming at them. Nevertheless, a pattern had been set: anti-aircraft warfare would employ heavy weapons to attack high-altitude targets and lighter weapons for use when aircraft came to lower altitudes. World War I demonstrated that aircraft could be an important part of the battlefield, but in some nations it

21147-441: The war was the first major German defeat in the Second World War. The Battle of Britain takes its name from the speech given by Prime Minister Winston Churchill to the House of Commons on 18 June: "What General Weygand called the 'Battle of France' is over. I expect that the Battle of Britain is about to begin." Strategic bombing during World War I introduced air attacks intended to panic civilian targets and led in 1918 to

21306-494: The war. It used a single interrogation frequency, like the Mark III, but differed in that it used a separate responder frequency. Responding on a different frequency has several practical advantages, most notably that the response from one IFF cannot trigger another IFF on another aircraft. But it requires a complete transmitter for the responder side of the circuitry, in contrast to the greatly simplified regenerative system used in

21465-440: The years immediately after World War I, the prospect of another major war seemed remote, particularly in Europe, where the most militarily capable nations were, and little financing was available. Four years of war had seen the creation of a new and technically demanding branch of military activity. Air defence had made huge advances, albeit from a very low starting point. However, it was new and often lacked influential 'friends' in

21624-563: Was a military campaign of the Second World War , in which the Royal Air Force (RAF) and the Fleet Air Arm (FAA) of the Royal Navy defended the United Kingdom (UK) against large-scale attacks by Nazi Germany 's air force, the Luftwaffe . It was the first major military campaign fought entirely by air forces. The British officially recognise the battle's duration as being from 10 July until 31 October 1940, which overlaps

21783-586: Was capable of providing data suitable for controlling AA guns, and the British Radar, Gun Laying, Mark I , was designed to be used on AA gun positions and was in use by 1939. The Treaty of Versailles prevented Germany having AA weapons, and for example, the Krupps designers joined Bofors in Sweden. Some World War I guns were retained and some covert AA training started in the late 1920s. Germany introduced

21942-569: Was desperately short of trained pilots and aircraft. Churchill sent fighter squadrons, the Air Component of the British Expeditionary Force , to support operations in France, where the RAF suffered heavy losses. This was despite the objections of its commander Hugh Dowding that the diversion of his forces would leave home defences under-strength. After the evacuation of British and French soldiers from Dunkirk and

22101-581: Was determined by time of flight, but the burning rate of the gunpowder was affected by altitude. The British pom-poms had only contact-fused ammunition. Zeppelins , being hydrogen-filled balloons, were targets for incendiary shells and the British introduced these with airburst fuses, both shrapnel type-forward projection of incendiary "pot" and base ejection of an incendiary stream. The British also fitted tracers to their shells for use at night. Smoke shells were also available for some AA guns, these bursts were used as targets during training. German air attacks on

22260-417: Was dialed into the unit. To start the identification procedure, the ground operator switched the pulse frequency of his radar from 3,750 Hz to 5,000 Hz. The airborne receiver decoded that and started to transmit the day code. The radar operator would then see the blip lengthen and shorten in the given code. The IFF transmitter worked on 168 MHz with a power of 400 watts (PEP). The system included

22419-404: Was electrical; the operator entered the target range and had displays at guns; it was used with their 75 mm. The British Wilson-Dalby gun director used a pair of trackers and mechanical tachymetry; the operator entered the fuse length, and deflection angles were read from the instruments. By the start of World War I , the 77 mm had become the standard German weapon, and came mounted on

22578-560: Was forbidden a military air force by the 1919 Treaty of Versailles , and therefore air crew were trained by means of civilian and sport flying . Following a 1923 memorandum, the Deutsche Luft Hansa airline developed designs for aircraft such as the Junkers Ju 52 , which could carry passengers and freight, but also be readily adapted into a bomber. In 1926, the secret Lipetsk fighter-pilot school began training Germans in

22737-407: Was holding out in hope of assistance from Russia, and the Soviet Union was to be invaded by mid 1941. Göring met his air fleet commanders, and on 24 July issued "Tasks and Goals" of firstly gaining air supremacy, secondly protecting invasion forces and attacking the Royal Navy's ships. Thirdly, they were to blockade imports, bombing harbours and stores of supplies. Hitler's "Directive No. 17 – For

22896-490: Was kept in operation during this period, but as the Battle ended, IFF Mark II was quickly put into full operation. Pip-squeak was still used for areas over land where CH did not cover, as well as an emergency guidance system. Even by 1940 the complex system of Mark II was reaching its limits while new radars were being constantly introduced. By 1941, a number of sub-models were introduced that covered different combinations of radars, common naval ones for instance, or those used by

23055-427: Was known as Mode A, and because they were identical, they are generally known as Mode 3/A. Several new modes were also introduced during this process. Civilian modes B and D were defined, but never used. Mode C responded with a 12-bit number encoded using Gillham code , which represented the altitude as (that number) x 100 feet - 1200. Radar systems can easily locate an aircraft in two dimensions, but measuring altitude

23214-440: Was not complete when the war ended. By the time testing was finished in 1948, the much improved Mark X was beginning its testing and Mark V was abandoned. Mark X started as a purely experimental device operating at frequencies above 1 GHz; the name refers to "experimental", not "number 10". As development continued it was decided to introduce an encoding system known as the "Selective Identification Feature", or SIF. SIF allowed

23373-582: Was probably first used by the UK when Air Defence of Great Britain (ADGB) was created as a Royal Air Force command in 1925. However, arrangements in the UK were also called "anti-aircraft", abbreviated as AA , a term that remained in general use into the 1950s. After the First World War it was sometimes prefixed by "light" or "heavy" (LAA or HAA) to classify a type of gun or unit. Nicknames for anti-aircraft guns include "AA", "AAA" or "triple-A" (abbreviations of "anti-aircraft artillery"), "flak" (from

23532-476: Was realised that range was the key to producing a better fuse setting. This led to the height/range finder (HRF), the first model being the Barr & Stroud UB2, a two-metre optical coincident rangefinder mounted on a tripod. It measured the distance to the target and the elevation angle, which together gave the height of the aircraft. These were complex instruments and various other methods were also used. The HRF

23691-532: Was received in silence, but he did not suggest negotiations and this was perceived as being effectively an ultimatum by the British government, which rejected the offer. Halifax kept trying to arrange peace until he was sent to Washington in December as ambassador, and in January 1941 Hitler expressed continued interest in negotiating peace with Britain. A May 1939 planning exercise by Luftflotte 3 found that

23850-525: Was replaced by the nine-foot optical base UB 7 and the eighteen-foot optical base UB 10 (only used on static AA sites). Goertz in Germany and Levallois in France produced five m (16 ft) instruments. However, in most countries the main effort in HAA guns until the mid-1930s was improving existing ones, although various new designs were on drawing boards. From the early 1930s eight countries developed radar ; these developments were sufficiently advanced by

24009-651: Was reported to Hitler, making peace negotiations seem feasible. Throughout July, as the battle started, the Germans made wider attempts to find a diplomatic solution. On 2 July, the day the armed forces were asked to start preliminary planning for an invasion, Hitler got von Ribbentrop to draft a speech offering peace negotiations. On 19 July Hitler made this speech to the German Parliament in Berlin, appealing "to reason and common sense", and said he could "see no reason why this war should go on". His sombre conclusion

24168-554: Was soon joined by the height/fuse indicator (HFI), this was marked with elevation angles and height lines overlaid with fuse length curves, using the height reported by the HRF operator, the necessary fuse length could be read off. However, the problem of deflection settings — "aim-off" — required knowing the rate of change in the target's position. Both France and the UK introduced tachymetric devices to track targets and produce vertical and horizontal deflection angles. The French Brocq system

24327-467: Was that the bomber will always get through , and that the only defence was a deterrent bomber force capable of matching retaliation. Predictions were made that a bomber offensive would quickly cause thousands of deaths and civilian hysteria leading to capitulation. However, widespread pacifism following the horrors of the First World War contributed to a reluctance to provide resources. Germany

24486-546: Was that destruction of enemy armed forces was of primary importance. The RAF responded to Luftwaffe developments with its 1934 Expansion Plan A rearmament scheme, and in 1936 it was restructured into Bomber Command , Coastal Command , Training Command and Fighter Command . The last was under Hugh Dowding , who opposed the doctrine that bombers were unstoppable: the invention of radar at that time could allow early detection, and prototype monoplane fighters were significantly faster. Priorities were disputed, but in December 1937,

24645-467: Was the earliest possible date and proposed postponement until the following year, but Hitler preferred September. He then told von Brauchitsch and Halder that he would decide on the landing operation eight to fourteen days after the air attack began. On 1 August, he issued Directive No. 17 for intensified air and sea warfare, to begin with Adlertag on or after 5 August, subject to weather, keeping options open for negotiated peace or blockade and siege. Under

24804-501: Was the guns protecting spotting balloons, in which case the altitude could be accurately measured from the length of the cable holding the balloon. The first issue was ammunition. Before the war it was recognised that ammunition needed to explode in the air. Both high explosive (HE) and shrapnel were used, mostly the former. Airburst fuses were either igniferious (based on a burning fuse) or mechanical (clockwork). Igniferious fuses were not well suited for anti-aircraft use. The fuse length

24963-496: Was the prospect of strategic air attack that was the main issue, presenting both a threat and an opportunity. The experience of four years of air attacks on London by Zeppelins and Gotha G.V bombers had particularly influenced the British and was one of if not the main driver for forming an independent air force. As the capabilities of aircraft and their engines improved it was clear that their role in future war would be even more critical as their range and weapon load grew. However, in

25122-428: Was to incapacitate the RAF so much that the UK would feel open to air attack, and would begin peace negotiations. It was also to isolate the UK and damage war production, beginning an effective blockade. Following severe Luftwaffe losses, Hitler agreed at a 14 September OKW conference that the air campaign was to intensify regardless of invasion plans. On 16 September, Göring gave the order for this change in strategy, to

25281-497: Was to increase attacks on shipping, economic targets and the RAF: air attacks and food shortages were expected to break morale and lead to capitulation. Destruction of the RAF was the first priority, and invasion would be a last resort. Göring's operational directive issued the same day ordered the destruction of the RAF to clear the way for attacks cutting off seaborne supplies to Britain. It made no mention of invasion. In November 1939,

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