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128-651: The Line proved very effective against initial RAF Bomber Command tactics. However, the RAF analyzed the German system and developed a counter-measure. On the night of 30/31 May 1942 in its 1,000 plane raid against Cologne , Bomber Command introduced the use of the bomber stream . The concentration of bombers through a few of the boxes ovewhelmed the Luftwaffe defenses. In response, the Germans converted their ground radar into

256-405: A Wellington of No. 115 Squadron from RAF Watton captained by Pilot Officer Jack Foster, who later said, "targets were found and bombed as never before". Krupp , the principal target, escaped bombing, but bombs did hit the southern areas of the city. In total, 33% of the aircraft reached the target area, an enormous advance over earlier results. The first completely successful Gee-led attack

384-401: A time base generator that started a "trace" moving quickly along the oscilloscope display. Any received signals caused the beam to deflect downward, forming a blip . The distance that the trace had moved from the left side of the display could be measured to accurately calculate the difference in time between sending and receiving, which, in turn, could be used to calculate the slant range to

512-631: A bombing aid, but it remained in use as a navigational aid in the UK area throughout and after the war. Gee remained an important part of the RAF's suite of navigation systems in the postwar era, and was included in aircraft such as the English Electric Canberra and the V-bomber fleet. It also had civilian use, and several new Gee chains were set up to support military and civil aviation across Europe. The system started to be shut down in

640-406: A common route and at the same speed to and from the target, each aircraft being allotted a height band and a time slot in a bomber stream to minimize the risk of collision. The first use of the bomber stream was the first 1,000 bomber raid against Cologne on the night of 30/31 May 1942. This tactic was extremely effective, leading to fighting between Kammhuber and Erhard Milch , his boss. Although

768-486: A disinformation campaign to hide the existence of the system. First, the use of the codename 'Gee' in communications traffic was dropped, and false communications were sent referring to a fictitious system called 'Jay'; it was hoped the similarity would cause confusion. A double agent in the Double Cross system reported to German Intelligence a fictional story of hearing a couple of RAF personnel talking carelessly in

896-499: A doctrine of "precision" bombing in daylight. When the German defences inflicted costly defeats on British raids in late 1939, a switch to night bombing was forced upon the Command. The problems of enemy defences were then replaced with the problems of night navigation and target-finding. In the early years of the war bombers had to rely on dead reckoning navigation supported by radio fixes and astro-navigation. Bomber Command comprised

1024-552: A fix was made from this chain over Turin in Italy, at a range of 730 miles (1,170 km). This remained the operational record for Gee, bested only by a freak reception over Gibraltar at a range of 1,000 miles (1,600 km). Counter-jamming efforts had already been considered, and resulted in the Gee Mk. II. This replaced the original receiver with a new model where the oscillators could be easily removed and swapped out to provide

1152-663: A group of elite, specially trained and experienced crews who flew ahead of the main bombing forces and marked the targets with flares and special marker-bombs. No. 8 Group controlled the Pathfinder squadrons. A number of other groups were part of the command, including, in June 1944, No. 26 Group RAF , three operational training groups – No. 91 Group RAF at Morton Hall, Swinderby, which was merged into No. 21 Group RAF , part of RAF Flying Training Command , on 1 May 1947; Nos 92 and 93 Groups ; and No. 100 Group RAF (of which last

1280-660: A high casualty rate: 55,573 were killed out of a total of 125,000 aircrew, a 44.4% death rate. A further 8,403 men were wounded in action, and 9,838 became prisoners of war. Bomber Command stood at the peak of its post-war military power in the 1960s, the V bombers holding the United Kingdom's nuclear deterrent and a supplemental force of Canberra light bombers. In 1968 it was merged with Fighter Command to form Strike Command . A memorial in Green Park in London

1408-653: A high priority, and the Chain Executive Committee was set up under the chairmanship of Robert Renwick in October 1941 to site a series of Gee stations. Gee was not the only solution being developed; it was soon joined by H2S radars and the Oboe system. As the initial availability of the Gee devices would be limited, the idea of the pathfinder force was adopted. This concept had originally been developed by

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1536-591: A hotel about Jay, and one dismissing it as it was "just a copy" of the German Knickebein system. Jones felt this would flatter the Germans, who might consider the information more reliable as a result. Extra antennae were added to the Gee transmitters to radiate false, unsynchronized signals. Finally, false Knickebein signals were transmitted over Germany. Jones noted all this appealed to his penchant for practical joking. In spite of these efforts, Jones initially calculated only 3 months would be needed before

1664-407: A large "Y" layout. A collection of such stations was known as a chain. The system was expected to operate over ranges around 100 miles (160 km), based on the widely held belief within the UK radio engineering establishment that the 30 MHz shortwave signals would have a relatively short range. With this sort of range, the system would be very useful as an aid for short-range navigation to

1792-411: A number of Groups . It began the war with Nos. 1 , 2 , 3 , 4 and 5 Groups. No. 1 Group was soon sent to France and then returned to Bomber Command control after the evacuation of France. No. 2 Group consisted of light and medium bombers who, although operating both by day and night, remained part of Bomber Command until 1943, when it was removed to the control of Second Tactical Air Force , to form

1920-518: A radar network which would follow the path of the British bombers, while a controller directed the night fighters into the stream. Measure and counter-measure continued until October 1944, when German defenses were no longer able to respond. The first version of the Line consisted of a series of radar stations with overlapping coverage, layered three deep from Denmark to the middle of France, each covering

2048-613: A raid got lost due to poor navigation and bombed London. Prime Minister Winston Churchill consequently ordered a retaliatory raid on the German capital of Berlin. The damage caused was minor but the raid sent Hitler into a rage. He ordered the Luftwaffe to level British cities, thus precipitating the Blitz . Like the United States Army Air Forces later in the war, Bomber Command had first concentrated on

2176-538: A range of about 30 kilometres (19 mi). Unlike the early-warning Freya, Würzburgs were accurate (and complex) tracking radars. One was locked onto the night fighter as soon as it entered the cell and as soon as the Freya picked up a target the second Würzburg locked onto it. All position reports were sent to the Himmelbett control centre thereby allowing controllers in the Himmelbett centre to get continual readings of

2304-543: A range of operational frequencies. These included the original 20–30 MHz band, as well as new bands at 40–50, 50–70, and 70–90 MHz. The navigator could replace these in flight, allowing reception from any active chain. Gee Mk. II went into operation in February 1943, at which point it had also been selected by the US 8th Air Force . On 23 April 1942, the go-ahead was given to develop mobile stations for Gee in preparation for

2432-454: A series of blips on the display. By measuring the distance between them, the delay between the two signals can be calculated. For instance, a receiver might measure the distance between the two blips to represent a delay of 0.5 ms. This implies that the difference in the distance to the two stations is 150 km. In this case, an infinite number of locations exist where that delay could be measured – 75 km from one station and 225 from

2560-453: A single line in space, down the runway centerline. In his new concept, charts would be produced illustrating not only the line of zero-difference, where the blips were superimposed like the landing system, but also a line where the pulses were received 1 μs apart, and another for 2 μs, etc. The result would be a series of lines arranged at right angles to the line between the two stations. A single pair of such transmitters would allow

2688-498: A time. For station identification, the A′ signals were only sent periodically. After the display was stabilized so the pulse trains were appearing in a single location on the screen, the A′ pulses could be seen blinking on and off with a set pattern (thus "ghosting" on the display). This allowed the operator to determine the identity of the master signal, and thus select the chain they wanted to use by positioning its associated A′ signal on

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2816-457: A timer. The other stations would be equipped with receivers listening for the signal arriving from the control station. When they received the signal, they would send out their own broadcasts. This would keep all the stations in synchronization, without the need for a wire between them. Dippy suggested building stations with a central "master" and three "secondaries" about 80 miles (130 km) away and arranged roughly 120 degrees apart, forming

2944-523: A total of 125,000 aircrew (a 44.4 per cent death rate), a further 8,403 were wounded in action and 9,838 became prisoners of war. This covered all Bomber Command operations. A Bomber Command crew member had a worse chance of survival than an infantry officer in World War I; more people were killed serving in Bomber Command than in the Blitz, or the bombings of Hamburg or Dresden. By comparison,

3072-437: A year lest the technique be adopted by the Germans and used against British cities. A more sophisticated method for blinding the German radar was " Mandrel ", a jamming signal broadcast from aircraft accompanying the bomber stream or later certain bombers themselves. This progressed into jamming techniques against individual German radar types and spoofing radars to see bomber streams that were not there. The British also attacked

3200-462: A zone about 32 kilometres (20 mi) long (north-south) and 20 kilometres (12 mi) wide (east-west). Each control centre was known as a Himmelbett (canopy bed) zone, consisting of a Freya radar with a range of about 100 kilometres (62 mi), a "master searchlight" directed by the radar, and a number of manually directed searchlights spread through the cell. Each cell was also assigned one primary and one backup night fighter. The fighter used

3328-412: Is considered. Consider two radio transmitters located at a distance of 300 km from each other, which means the radio signal from one will take 1  millisecond to reach the other. One of these stations is equipped with an electronic clock that periodically sends out a trigger signal. When the signal is sent, this station, A , sends out its transmission. A millisecond later, that signal arrives at

3456-421: Is known as a "chain". Gee chains used an arrangement with one master and two or three slaves. The transmitters had a power output around 300  kW and operated in four frequency bands between 20 and 85  MHz . The Gee signal for any given chain consisted of a series of pulses of radio signal with a roughly inverted-parabolic envelope about 6  microseconds in duration. In a three station system,

3584-645: The Advanced Air Striking Force . This action had two aims: to give the British Expeditionary Force some air-striking power and to allow the Battles to operate against German targets, since they lacked the range to do so from British airfields. In May 1940, some of the Advanced Air Striking Force was caught on the ground by German air attacks on their airfields at the opening of the invasion of France. The remainder of

3712-400: The A′ double pulse allowed the order sequence to be identified by the navigator operating the receiver. The whole sequence repeated on a 4 ms cycle (i.e. 250 times per second), with the pattern A-B-A′-C . In the case of a four station system, the cycle above would be repeated, with the addition of the D station, which would broadcast another double pulse. To allow this to be identified,

3840-526: The Battle of the Ruhr on Essen. The bombers destroyed 160 acres (65 ha) of the city and hit 53 Krupps buildings. The Battle of Hamburg in mid-1943 was one of the most successful Bomber Command operations, although Harris' extension of the offensive into the Battle of Berlin failed to destroy the capital and cost his force more than 1,000 crews in the winter of 1943–44. In August 1943, Operation Hydra ,

3968-545: The Butt report , which demonstrated only 5% of the bombs sent out on a mission landed within 5 mi (8 km) of their targets. With these statistics, any sort of strategic campaign based on attacks against factories and similar targets was hopeless. This led to Frederick Lindemann 's notorious " dehousing " paper, which called for the bomber efforts to be used against the houses of the German citizens to break their ability to work and will to resist. This became official policy of

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4096-513: The D station was timed at 166 times per second, such that its pulse would move from the A-B trace to the A'-C trace, not appearing on either trace and back to the A-B trace. The cycle therefore was A-B-D-A′-C-A-B-A′-C-D-A-B-A′-C... . The D pulse appearing on both traces meant that a fix could be made using the combinations AB/AC , AB/AD , or AC/AD , giving a wider area of high precision coverage than

4224-525: The Royal Air Force during World War II . It measured the time delay between two radio signals to produce a fix , with accuracy on the order of a few hundred metres at ranges up to about 350 miles (560 km). It was the first hyperbolic navigation system to be used operationally, entering service with RAF Bomber Command in 1942. Gee was devised by Robert Dippy as a short-range blind-landing system to improve safety during night operations. In

4352-646: The Royal Air Force 's bomber forces from 1936 to 1968. Along with the United States Army Air Forces , it played the central role in the strategic bombing of Germany in World War II . From 1942 onward, the British bombing campaign against Germany became less restrictive and increasingly targeted industrial sites and the civilian manpower base essential for German war production. In total 501,536 operational sorties were flown, 2.25  billion pounds (1.02 million tonnes ) of bombs were dropped and 8,325 aircraft lost in action. Bomber Command crews also suffered

4480-528: The Ruhr , including oil plants and other civilian industrial targets which aided the German war effort, such as blast furnaces (which were visible at night). The first attack took place on the night of 15/16 May, with 96 bombers setting off to attack targets east of the Rhine, 78 of which were against oil targets. Of these, only 24 claimed to have found their targets. Bomber Command itself soon fully joined in

4608-528: The Short Sperrin fall-back design. Multiple designs were tried out because no one could predict which designs would be successful at the time. The V bombers became the backbone of the British nuclear forces and comprised the Valiant, Handley Page Victor (in service in 1958) and Avro Vulcan (1956). Gee (navigation) Gee , sometimes written GEE , was a radio-navigation system used by

4736-468: The larger British bombs were highly destructive. 15 years after the war's end, Speer was unequivocal about the effect, The real importance of the air war consisted in the fact that it opened a second front long before the invasion in Europe ;... Defence against air attacks required the production of thousands of anti-aircraft guns, the stockpiling of tremendous quantities of ammunition all over

4864-568: The light bomber component of that command. Bomber Command also gained two new groups during the war: the Royal Canadian Air Force (RCAF) squadrons were organised into No. 6 Group and the Pathfinder Force was expanded to form No. 8 (Pathfinder) Group from existing squadrons on 8 January 1943. Many squadrons and personnel from Commonwealth and other European countries flew in Bomber Command. No. 6 Group, which

4992-407: The "fast" time base position for the decimal readings, followed by the whole numbers which would be read with the display in the "Main" time base setting. The respective numbers from the A-B and A′-C Readings would be plotted on a lattice chart. Signals from different chains were closely spaced in frequency, close enough that the wide-band R1355 receiver would often tune in more than one chain at

5120-752: The "heavies". After the end of the war in Europe, Britain planned to send Lancasters to the Japanese theatre as part of Tiger Force and to use Gee for the passage of flights to Asia. Preparations began for Gee transmitters in Nablus (in Palestine) guiding the flights across the Middle East, but the surrender of Japan removed the need for this chain. This work was being carried out by MEDME, Cairo, under Air Vice-Marshal R. S. Aitken. German bombers also used

5248-407: The "real" stream appeared hundreds of miles away, too far to be attacked. The first time this was used was during Operation Gomorrah (a week-long bombing campaign against Hamburg ) and proved spectacularly effective. The German radar operators eventually learned to spot the lead bombers at the edge of the windowing, making it less effective. The British had held back from introducing Window for over

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5376-512: The 1930s, the development of radar demanded devices that could accurately measure these sorts of signal timings. In the case of Chain Home , transmission aerials sent out signals, and any reflections from distant targets were received on separate aerials. An oscilloscope (or oscillograph as it was known in the UK) was used to measure the time between transmission and reception. The transmitter triggered

5504-466: The 88 mm gun was an effective AA weapon, it was also a deadly destroyer of tanks, and lethal against advancing infantry. These weapons would have done much to augment German anti-tank defences on the Russian front. Mine laying operations were a major contribution to the disruption of German naval activities. Aerial minelaying was used on the iron ore routes from Scandinavia and U-boat training areas in

5632-520: The Baltic; in North-West Europe aerial mines sank seven times more ships than naval mines laid from ships. In operations Bomber Command laid 47,278 mines while losing 468 aircraft; Coastal Command contribution was 936 mines. Bomber Command and Coastal Command minelaying is credited with the loss of 759 vessels totalling 1.62 billion pounds (0.73 million tonnes). German production

5760-549: The Battle of the Ruhr marked a turning point in the history of the German war economy .... and that in the first quarter of 1943 steel production fell by 448 million pounds (203,209 tonnes), leading to cuts in the German ammunition production programme and a sub-components crisis ( Zulieferungskrise ). German aircraft output did not increase between July 1943 and March 1944: Bomber command had stopped Speer's armaments miracle in its tracks. The greatest contribution to winning

5888-565: The Battles proved to be horrendously vulnerable to enemy fire. Many times, Battles would set out to attack and be almost wiped out in the process. e.g. 10 May 1940 when a significant number of Battles were shot down or damaged. Following the Rotterdam Blitz of 14 May, RAF Bomber Command was authorized to attack German targets east of the Rhine on 15 May; the Air Ministry authorized Air Marshal Charles Portal to attack targets in

6016-722: The British bombing component was intended to be based on Okinawa . Bomber Command groups were re-organised for Operation Downfall but the Soviet invasion of Manchuria and the Bombing of Hiroshima and Nagasaki occurred before the force had been transferred to the Pacific. In Europe Bomber Command's final operation was to fly released Allied prisoners of war home to Britain in Operation Exodus . Bomber Command crews suffered an extremely high casualty rate: 55,573 killed out of

6144-581: The British survey found that actual arms production decreases were a mere 3 per cent for 1943, and 1 per cent for 1944. However they did find decreases of 46.5 per cent and 39 per cent in the second half of 1943 and 1944 respectively in the metal processing industries. These losses resulted from the devastating series of raids the Command launched on the Ruhr Valley . A contrasting view was offered by Adam Tooze that by referring to contemporary sources rather than post-war accounts: there can be no doubt that

6272-581: The French were even more concerned lest Bomber Command operations provoke a German bombing attack on France. Since the Armée de l'Air had few modern fighters and no defence network comparable to the British Chain Home radar stations, this left France powerless before the threat of a German bombing attack. The final problem was lack of adequate aircraft. The Bomber Command workhorses at the start of

6400-563: The Freya radar operators directed the master searchlight to illuminate the plane. Once this had happened other manually controlled searchlights also picked up the plane, and the night fighters were directed to intercept the illuminated bomber. Demands by the Bürgermeisters in Germany led to the recall of the searchlights to the major cities, which undermined this system. Later versions of the Himmelbett added two Würzburg radars , with

6528-411: The Gee system for attacks on the UK; captured Gee receivers provided the electronics. Later in the war, Bomber Command wanted to deploy a new navigation system not for location fixing, but to mark a single spot in the air. This location would be used to drop bombs or target indicators for strikes by other bombers. The Oboe system provided this already; Oboe sent an interrogation signal from stations in

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6656-608: The Germans were found to have developed a series of radio aids for this, notably the X-Gerät system. The RAF initially pooh-poohed this approach, claiming it only demonstrated the superiority of the RAF's training. By late 1940 a number of reports were trickling back from observers in the field, who were noting that Allied bombers did not appear to be bombing their targets. In one instance, bombs reportedly fell over 50 mi (80 km) from their target. For some time, these results were dismissed, but calls for an official enquiry led to

6784-504: The Germans would be able to jam the system. As it turns out, jamming was not encountered until five months into the campaign, and it was much longer before it became a serious concern. Even with limited testing, Gee proved itself to be easy to use and more than accurate enough for its tasks. On 18 August 1941, Bomber Command ordered Gee into production at Dynatron and Cossor , with the first mass-produced sets expected to arrive in May 1942. In

6912-500: The Luftwaffe for their early night raids against England. Lacking enough radio sets and the widespread training to place their radio navigation systems on all their aircraft, they collected what they had into the single group, KG100 . KG100 would then use their equipment to drop flares, which acted as an aiming point for following bombers. Eager to test the Gee system, prototype sets were used on target indicator aircraft well before

7040-462: The North Sea from Britain to Holland, en route to Germany. The first serious jamming was encountered on the night of 4/5 August 1942. This grew in strength as the bombers approached their target at Essen, and the signals became unusable at 10 to 20 miles (16–32 km) from the target. The newly formed southern chain was not yet known to the Germans and continued to be useful. On 3/4 December,

7168-583: The Pathfinders, the de Havilland Mosquito , also made its appearance. By 25 July 1943, the Bomber Command headquarters had come to occupy "a substantial set of red brick buildings, hidden in the middle of a forest on top of a hill in the English county of Buckinghamshire". An offensive against the Rhine-Ruhr area ("Happy Valley" to aircrew) began on the night of 5/6 March 1943, with the first raid of

7296-589: The RAF as Boeing Washingtons, to supplement the Avro Lincoln , a development of the Lancaster. The first jet bomber, the English Electric Canberra light bomber, became operational in 1951. Some Canberras remained in RAF service up to 2006 as photo-reconnaissance aircraft. The model proved an extremely successful aircraft; Britain exported it to many countries and licensed it for construction in Australia and

7424-476: The RAF in 1942. While the debate raged, Bomber Command dramatically lowered their sortie rate, awaiting the rebuilding of the force with the newly arriving 4-engine "heavies" such as the Handley Page Halifax and Avro Lancaster , and the deployment of Gee. The two, combined, would offer the accuracy and weight of bombs that Lindemann's calculations called for. Efforts to test and deploy Gee became

7552-456: The Rhineland, bombed on 16, 17, 18 and 19 February, was bombed again on 23 March, leaving the city "97 percent destroyed". The last raid on Berlin took place on the night of 21/22 April, when 76 Mosquitos made six attacks just before Soviet forces entered the city centre. By this point, most RAF bombing operations were for the purpose of providing tactical support. The last major strategic raid

7680-464: The UK out to the northeastern corner of Scotland. These were joined by a further two chains in France, and a single chain in the UK occupation zone in northern Germany. Hyperbolic navigation systems can be divided into two main classes: those that calculate the time difference between two radio pulses, and those that compare the phase difference between two continuous signals. Here, only the pulse method

7808-414: The UK, "reflected" them from transceivers on the aircraft, and timed the difference between the two signals using equipment similar to Gee. However, Oboe had the major limitation that it could only guide a single aircraft at a time and took about 10 minutes to guide a single aircraft to its target. A system able to guide more aircraft at once would be a dramatic improvement. The result was a new version of

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7936-666: The US Eighth Air Force , which flew daylight raids over Europe, had 350,000 aircrew during the war and suffered 26,000 killed and 23,000 POWs. Of the RAF Bomber Command personnel killed during the war, 72 per cent were British, 18 per cent were Canadian, 7 per cent were Australian and 3 per cent were New Zealanders. Taking an example of 100 airmen: In total 501,536 operational sorties were flown, 2.25 billion pounds (1.02 million tonnes) of bombs were dropped and 8,325 aircraft lost in action. Harris

8064-635: The United States. The joint US-UK Project E was intended to make nuclear weapons available to Bomber Command in an emergency, with the Canberras the first aircraft to benefit. The next jet bomber to enter service was the Vickers Valiant in 1955, the first of the V bombers . The Air Ministry conceived of the V bombers as the replacement for the wartime Lancasters and Halifaxes. Three advanced aircraft were developed from 1946, along with

8192-605: The action; in the Battle of Britain , Bomber Command was assigned to bomb invasion barges and fleets assembling in the Channel ports. This was much less public than the battles of the Spitfires and Hurricanes of RAF Fighter Command but still vital and dangerous work, carried out night after night. Bomber Command was also indirectly responsible, in part at least, for the switch of Luftwaffe attention away from Fighter Command to bombing civilian targets. A German bomber on

8320-467: The aircraft to determine on which line they were, but not their location along it. For this purpose, a second set of lines from a separate station would be required. Ideally, these lines would be at right angles to the first, producing a two-dimensional grid that could be printed on navigational charts. To ease deployment, Dippy noted that the station in the centre could be used as one side of both pairs of transmitters if they were arranged like an L. Measuring

8448-400: The airport, as well as helping bombers form up at an arranged location after launch. Additionally, after flying to their cruising altitude, the bombers could use Gee fixes to calculate the winds aloft, allowing them to more accurately calculate dead reckoning fixes after the aircraft passed out of Gee range. Experimental systems were being set up in June 1940. By July, to everyone's delight,

8576-420: The bomber stream would overwhelm the six potential interceptions per hour that the German night fighters could manage in a Himmelbett zone. It was then a matter of calculating the statistical loss from collisions against the statistical loss from night fighters to calculate how close the bombers should fly to minimise RAF losses. The introduction of Gee radio navigation in 1942 allowed the RAF bombers to fly by

8704-480: The bombers proved extremely vulnerable to both ground fire and attacking fighters . After some discussion, the best course of action was decided to be to return to night bombing, which had been the primary concept earlier in the 1930s. This raised the need for better landing aids, and for night navigation aids in general. Dippy refined his system for this purpose, and formally presented a new proposal on 24 June 1940. The original design used two transmitters to define

8832-527: The bombing of the Peenemünde V-2 rocket facility opened the secondary Operation Crossbow campaign against long-range weapons. By April 1944, Harris was forced to reduce his strategic offensive as the bomber force was directed (much to his annoyance) to tactical and transport targets in France in support of the invasion of Normandy . The transport offensive proved highly effective. By late 1944, bombing such as Operation Hurricane (to demonstrate

8960-436: The bottom left. At long ranges the hyperbolic lines approximate straight lines radiating from the center of the baseline. When two such signals from a single chain are considered, the resulting pattern of lines becomes increasingly parallel as the baseline distance becomes smaller in comparison to the range. Thus at short distances the lines cross at angles close to 90 degrees, and this angle steadily reduces with range. As

9088-548: The capabilities of the combined British and US bomber forces), competed against the German defences . Bomber Command was now capable of putting 1,000 aircraft over a target without extraordinary efforts. Within 24 hours of Operation Hurricane, the RAF dropped about 22 million pounds (10,000 tonnes) of bombs on Duisburg and Brunswick , the greatest bomb load dropped in a day during the Second World War. Wesel in

9216-756: The communications between ground stations and fighters, with Operation Corona , broadcasting false directions in authentic accents over the radio. One other element was long-range nightfighters operating against the German nightfighters, using a system called " Serrate " to home in on the German nightfighter radar signals. At least three squadrons equipped with Bristol Beaufighter and de Havilland Mosquito were part of No. 100 Group RAF supporting Bomber Command with electronic countermeasures. RAF Bomber Command 1942: Manchester , Stirling , Halifax , Lancaster , Mosquito . 1945: Lincoln 1950: Washington B.1 1951: Canberra . 1955: Vickers Valiant 1956: Avro Vulcan RAF Bomber Command controlled

9344-482: The country, and holding in readiness hundreds of thousands of soldiers, who in addition had to stay in position by their guns, often totally inactive, for months at a time ... No one has yet seen that this was the greatest lost battle on the German side. In terms of production decrease resulting from the RAF area attacks, the US survey, based upon limited research, found that in 1943 it amounted to 9 per cent and in 1944 to 17 per cent. Relying on US gathered statistics,

9472-547: The course of development by the Telecommunications Research Establishment (TRE) at Swanage , the range was found to be far better than expected. It then developed into a long-range, general navigation system. For large, fixed targets, such as cities that were attacked at night, Gee offered enough accuracy to be used as an aiming reference without the need to use a bombsight or other external references. Jamming reduced its usefulness as

9600-471: The display, and show the A and A′ pulses above the inverted B and C pulses respectively. The fine adjustment would be used to position the B pulse directly beneath the A pulse, and the C pulse directly beneath the A′ pulse. A switch, referred to as the "clearing switch", was thrown, and the time of the fix noted. The clearing switch changed the display from displaying the pulses to displaying an internally generated scale. This scale would be read in

9728-455: The display. The description below is with reference to a three station system, but the D pulse would be substituted for either the B or C pulse in a four station system. In the "Main" time base setting, the CRT display was configured to display the signal across two lines (each showing half of the time of the signal). A local oscillator of much less complexity than the one at the master station

9856-525: The entire UK, three Gee chains were constructed under the direction of Edward Fennessy . The original chain started continuous operation on 22 June 1942, followed by a chain in Scotland later that year, and the southwest chain in 1943. Even as German jamming efforts took hold, Gee remained entirely useful as a short-range navigation system over the UK. Only 1.2% of Gee-equipped aircraft failed to return to their base, as opposed to 3.5% of those without it. Gee

9984-512: The invasion of Europe. This would not only extend the range of the system eastward, but also allow stations to move and suddenly appear elsewhere if jamming became an issue. The first of an eventual three such mobile chains was formed up on 22 November 1943. This was put into operation on 1 May 1944 at Foggia in Italy, and was used operationally for the first time on 24 May. Other units were sent into France soon after D-Day . The mobile units in France and Germany were later replaced by fixed stations,

10112-402: The late 1930s, this statement was effectively true. Attacking bombers could not be detected early enough to assemble fighters fast enough to prevent them reaching their targets. Some damage might be done to the bombers by anti-aircraft (AA) guns, and by fighters as the bombers returned to base, but that was not as effective as a proper defence. Consequently, the early conception of Bomber Command

10240-434: The late 1960s, with the last station going off the air in 1970. Gee inspired the original LORAN ("Loran-A") system. The basic idea of radio hyperbolic navigation was well known in the 1930s, but the equipment needed to build it was not widely available at the time. The main problem involved the accurate determination of the difference in timing of two closely spaced signals, differences in milli- and microseconds. During

10368-417: The master sent a single pulse, referred to as A , followed 2  milliseconds (ms) later by a double pulse, A′ (A Prime). The first slave station sent a single pulse 1 ms after the master's single pulse, labeled B , and the second slave sent a single pulse 1 ms after the master's double pulse, labeled C . As the receiver did not have any means of automatically synchronizing to the master signal,

10496-405: The meantime, a separate order for 300 hand-made sets was placed for delivery on 1 January 1942, which was later pushed back to February. Overall, 60,000 Gee sets were manufactured during World War II, used by the RAF, USAAF , and Royal Navy . The first operational mission using Gee took place on the night of 8/9 March 1942, when a force of about 200 aircraft attacked Essen . It was installed on

10624-514: The nature of the Kammhuber Line and started studying ways to defeat it. At the time RAF Bomber Command exerted no discipline on how pilots were to get their aircraft to the target. There was an air of amateurism and individuality to the pilots of Bomber Command. Each pilot was on his own as to his flight path to the target, altitude to be flown and time of arrival. Thus bombing attacks would go on sporadically for four or five hours, and there

10752-417: The night of 11/12 August, two Gee-equipped aircraft using Gee coordinates only delivered "uncanny accuracy" when dropping their bombs. However, on the next night on a raid over Hanover , a Gee-equipped Vickers Wellington was lost. The Gee set did not contain self-destruct systems, and it might have fallen into German hands. Operational testing was immediately suspended. R. V. Jones responded by starting

10880-504: The order of the previous year instructing Bomber Command to conserve its forces; this resulted in a large campaign of area bombardment against the Ruhr area. Professor Frederick Lindemann 's "de-housing" paper of March identified the expected effectiveness of attacks on residential and general industrial areas of cities. The aerial bombing of cities such as the Operation Millennium raid on Cologne continued throughout

11008-473: The other, or 150 km from one and 300 from the other, and so on. When plotted on a chart, the collection of possible locations for any given time difference forms a hyperbolic curve. The collection of curves for all possible measured delays forms a set of curved radiating lines, centred on the line between the two stations, known as the "baseline". To take a fix, the receiver takes two measurements based on two different pairs of stations. The intersections of

11136-486: The positions of both planes. A Jägerleitoffizier directed the German night-fighter to a visual interception with the RAF bomber using radio. Operations were manually coordinated using an "Auswertetisch" (the precursor of a " Seeburg " plotting table). To aid interception a number of the night fighters were fitted with a short-range infrared device known as the Spanner-Anlage but these proved almost useless. Later

11264-499: The production sets were available in the number required for large raids. On 15 May 1941, such a set provided an accurate fix at a range of 400 miles (640 km) at an altitude of 10,000 feet (3,000 m). The first full transmitter chain was completed in July 1941, but in testing over the North Sea, the sets proved to be unreliable. This was traced to the power supplies and tubes, and corrections were designed and proved that summer. On

11392-402: The rates started to improve – for the Germans – they introduced " Window ". When they dropped strips of foil from "lead" bombers, the German radar operators saw what appeared to be a stream entering their box, each packet of chaff appearing to be a bomber on their displays. Night fighters were then sent to attack this stream, only to find empty space. Just as the fighters reached the false stream,

11520-423: The required accuracy and coverage. The single-transmitter, multiple-antenna solution of the original proposal was no longer appropriate, especially given that the stations would be located far apart and wiring to a common point would be difficult and expensive. Instead, Dippy described a new system using individual transmitters at each of the stations. One of the stations would periodically send out its signal based on

11648-548: The rest of the war, culminating in the controversial bombing of Dresden in 1945. In 1942, the main workhorse-aircraft of the later part of the war came into service: the four-engined heavies. The Halifax and Lancaster made up the backbone of the Command; they had a longer range, higher speed and much greater bomb load than earlier aircraft. The older four-engined Short Stirling and twin-engined Vickers Wellington bombers were not taken out of service, but moved to less demanding tasks such as mine-laying. The classic aircraft of

11776-515: The same basic Oboe concept, but reversed so that it was driven by the aircraft and reflected from ground-based transceivers. This would require equipment on the aircraft that could receive and measure the time difference between two signals. The reuse of the existing Gee equipment for this purpose was obvious. The new Gee-H system only required a single modification, the addition of a new transmitter that would send signals out for reflection from ground-based transceivers. With this transmitter turned off,

11904-403: The same point on the display. If the aircraft were located to one side or the other, one of the signals would be received before the other, forming two distinct peaks on the display. By determining which signal was being received first, pilots would know that they were closer to that antenna, and would be able to recapture the proper direction by turning away from it. Watt liked the idea, but at

12032-407: The same timing. The pulses would be identified, then the oscillator control was adjusted to bring the double A′ pulses to the left of the bottom trace. Rotary Switches followed by fine adjustment were used to position markers under the B and C pulses (the markers would invert the pulses on the display), and then the time base was switched to a "fast" position, which would add additional lines to

12160-451: The second station, B . This station is equipped with a receiver, and when it sees the signal from A arrive, it triggers its own transmitter. This ensures that stations send out signals precisely 1 ms apart, without the second station needing to have an accurate timer of its own. In practice, a fixed time is added to account for delays in the electronics. A receiver listening for these signals and displaying them on an oscilloscope sees

12288-489: The sextant was sufficient. ) The fourth problem was the limited accuracy of bombing, especially from high level. When the war began on 1 September 1939, Franklin D. Roosevelt , President of the neutral United States, issued an appeal to the major belligerents to confine their air raids to military targets. The French and British agreed to abide by the request, provided "that these same rules of warfare will be scrupulously observed by all of their opponents". British policy

12416-476: The short-range, UHF-band original version of the Lichtenstein airborne intercept radar system was added to the aircraft, allowing them to detect aircraft once the operators had directed them into the area, making searchlights largely redundant. The battle stations were known as "Kammhuber's opera houses" and procedures developed in 1942 were used until the end of the war. British intelligence soon discovered

12544-415: The success rate of the line dropped, the network of radars and plotting stations continued to prove their worth. Now when a raid started, night fighters from any base within range were directed into the stream, where it was hoped they would be able to find aircraft with their radar. At the same time a massive building program started to add hundreds of Würzburgs to the system, although the infrastructure needed

12672-480: The system clearly was usable to at least 300 miles (480 km) at altitudes of 10,000 feet (3.0 km). On 19 October, a fix was made at 110 miles (180 km) at 5,000 feet. The discovery of Gee's extended range arrived at a pivotal point in the RAF's bombing campaign. Having originally relied on day bombing, the RAF had not invested a tremendous amount of effort on the navigation skills needed for night flying. When The Blitz night-bombing offensive started,

12800-504: The system reverted to being a normal Gee unit. This allowed it to be used in Gee-H mode during attacks, and then Gee mode for navigation back to their home airfields. Gee was of such great utility that the hurried deployments during the war were rationalized as the basis for an ongoing and growing navigational system. The result was a set of four chains, South Western, Southern, Scottish, and Northern, which have continuous coverage over most of

12928-405: The target. Radar can also be used as a navigation system. If two stations are able to communicate, they could compare their measurements of the distance to a target, and use basic trilateration to determine the location. This calculation could then be sent to the aircraft by radio. This is a fairly manpower-intensive operation, and while it was used by both the British and Germans during the war,

13056-449: The three station system. The triggering of the A pulses was timed at 150 kHz by a stable local oscillator at the master station, but the timing was sometimes deliberately changed. The time for ten cycles of this 150 kHz oscillation, 66.66 μs, was called a Gee unit and corresponded to a range difference of 12.4 miles (20.0 km). On board the aircraft, the signals from the three or four stations were received and sent to

13184-431: The time delays of the two outlier stations relative to the centre, and then looking up those numbers on a chart, an aircraft could determine its position in space, taking a fix. The gridded lines on the charts gave the systems its name, "Gee" for the "G" in "Grid". As the system was now intended to offer navigation over a much wider area, the transmitters of a single station would have to be located further apart to produce

13312-625: The time, a pressing need for the system was not apparent. At the time, the RAF relied on daylight bombing by tight formations of heavily defended bombers as its primary attack force, so night landings were not a major concern. Landing aids would be useful, but radar work was the more urgent need. The RAF's bombing campaign plans quickly went awry, especially after the Air Battle of the Heligoland Bight in 1939. Contrary to prewar thinking,

13440-431: The two antennas would send a common signal over transmission lines to the two antennas, which ensured that both antennas would broadcast the signal at the same instant. A receiver in the aircraft would tune in these signals and send them to an A-scope -type display, like those used by Chain Home. If the aircraft were properly lined up with the runway, both signals would be received at the same instant, and thus be drawn at

13568-504: The two sets of curves normally results in two possible locations, equal distance on either side of the midpoint of the baseline. Using some other form of navigation, dead reckoning for instance, one can eliminate one of these possible positions, thus providing an exact fix. Instead of using two separate pairs of stations, the system can be simplified by having a single master and two secondaries located some distance away from each other so their patterns overlap. A collection of such stations

13696-499: The war made by Bomber Command was in the huge diversion of German resources into defending the homeland. By January 1943 some 1,000 Luftwaffe night fighters were committed to the defence of the Reich; mostly twin engined Messerschmitt Bf 110 and Junkers Ju 88 . Most critically, by September 1943, 8,876 of the deadly, dual purpose 88 mm guns were also defending the homeland with a further 25,000 light flak guns, 20/37 mm. Though

13824-615: The war, the Vickers Wellington , Armstrong Whitworth Whitley and Handley Page Hampden/Hereford , had been designed as tactical-support medium bombers and none of them had enough range or ordnance capacity for anything more than a limited strategic offensive. Of these the Wellington had the longest range at 2,550 miles (4,100 km). Bomber Command became even smaller after the declaration of war. No. 1 Group , with its squadrons of Fairey Battles , left for France to form

13952-485: The workload meant it could generally only be used to guide single aircraft. In October 1937, Robert (Bob) J. Dippy, working at Robert Watson-Watt 's radar laboratory at RAF Bawdsey in Suffolk , proposed using two synchronized transmitters as the basis for a blind landing system. He envisaged two transmitting antennas positioned about 10 miles (16 km) apart on either side of a runway. A transmitter midway between

14080-581: Was activated on 1 January 1943, was unique among Bomber Command groups, in that it was not an RAF unit; it was a Canadian unit attached to Bomber Command. At its peak strength, 6 Group consisted of 14 operational RCAF bomber squadrons and 15 squadrons served with the group. No. 8 Group, also known as the Pathfinder Force, was activated on 15 August 1942. It was a critical part of solving the navigational and aiming problems experienced. Bomber Command solved its navigational problems using two methods. One

14208-439: Was advised by an Operational Research Section (ORS-BC) under a civilian, Basil Dickins, supported by a small team of mathematicians and scientists. ORS-BC (under Reuben Smeed ) was concerned with analysing bomber losses. They were able to influence operations by identifying successful defensive tactics and equipment, though some of their more controversial advice (such as removing ineffectual turrets from bombers to increase speed)

14336-467: Was as an entity that threatened the enemy with utter destruction. The Italian general Giulio Douhet , author of The Command of the Air , was of that view. In 1936, Germany's increasing air power was feared by British government planners who commonly overestimated its size, reach and hitting power. Planners used estimates of up to 72 British deaths per tonne (2,200 lb) of bombs dropped, though this figure

14464-460: Was carried out on 13/14 March 1942 against Cologne . The leading crews successfully illuminated the target with flares and incendiaries and the bombing was generally accurate. Bomber Command calculated that this attack was five times more effective than the earlier raid on the city. The success of Gee led to a change in policy, selecting 60 German cities within Gee range for mass bombing using 1,600–1,800 tons of bombs per city. To provide coverage of

14592-594: Was considered so important that an unserviceable Gee set would ground an aircraft. One illustration of Gee's routine employment by Bomber Command in navigation tasks was its use (albeit a limited one) in Operation Chastise (commonly known as the "Dam Buster Raid") in May 1943. In his memoir, Enemy Coast Ahead , Guy Gibson , the leader of the raid, briefly mentions his navigator, F/O 'Terry' Taerum, RCAF , employing what Gibson calls Taerum's "G Box" to determine groundspeed while flying very low at night over

14720-422: Was diverted into construction and manning of minesweepers and the deployment of flak batteries to protect ports and estuaries. Around 100 vessels, mostly cargo types and around 11 million pounds (5,080 tonnes), were converted to Sperrbrecher mine barrage breakers to sail ahead of ships leaving harbour and of these about half of were lost to mines. Bomber Command acquired B-29 Superfortresses , known to

14848-496: Was extensive. The boxes were initially the radius of the Würzburg radars, about 22 miles (35 km), but more powerful radar later on made the boxes up to 100 miles (160 km) across. Eventually, the line of boxes was several deep, especially around larger towns and the Ruhr valley . Once again the system started to score increasing successes against the British raids. The British were ready for this development, and as soon as

14976-461: Was grossly exaggerated. As well, the planners did not know that German bombing aircraft of the day (not quite 300 Junkers Ju 52 medium bombers) did not have the range to reach the UK with a load of bombs and return to the mainland. British air officers did nothing to correct these perceptions because they could see the usefulness of having a strong bombing arm. At the start of the Second World War in 1939, Bomber Command faced four problems. The first

15104-515: Was ignored. The very high casualties suffered give testimony to the dedication and courage of Bomber Command aircrew in carrying out their orders. The overall loss rate for Bomber Command operations was 2.2 per cent, but loss rates over Germany were significantly higher; from November 1943 – March 1944, losses averaged 5.1 per cent. The highest loss rate (11.8 per cent) was incurred on the Nuremberg raid (30 March 1944). The disparity in loss rates

15232-546: Was lack of size; Bomber Command was not large enough effectively to operate as an independent strategic force. The second was rules of engagement; at the start of the war, the targets allocated to Bomber Command were not wide enough in scope. The third problem was the Command's lack of technology; specifically radio or radar derived navigational aids to allow accurate target location at night or through cloud. (In 1938, E. G. "Taffy" Bowen proposed using ASV radar for navigation, only to have Bomber Command disclaim need for it, saying

15360-421: Was no concentration in the bombing. The boxes of the Kammhuber Line were well set up to deal with the broad approach paths of individual bombers. At the urging of R. V. Jones , Bomber Command reorganized their attacks into streams of bombers – the so-called bomber stream, carefully positioned so the stream flew down the middle of a single cell. Data provided to the British scientists allowed them to calculate that

15488-716: Was reflected in that, at times, Bomber Command considered making sorties over France only count as a third of an op towards the "tour" total and crews derisively referred to officers who only chose to fly on the less dangerous ops to France as "François". The loss rates excluded aircraft crashing in the UK on return, even if the machine was a write-off and there were crew casualties, which amounted to at least another 15 percent. Losses in training were significant and some courses lost 25 per cent of their intake before graduation; 5,327 men were killed in training from 1939 to 1945. RAF Bomber Command had 19 Victoria Cross recipients . Albert Speer , Hitler's Minister of Armaments, noted that

15616-516: Was responsible for development, operational trial and use of electronic warfare and countermeasures equipment). In 1941, the Butt Report revealed the extent of bombing inaccuracy: Churchill noted that "this is a very serious paper and seems to require urgent attention". The Area Bombing Directive of 14 February 1942 ordered Bomber Command to target German industrial areas and the "morale of...the industrial workers". The directive also reversed

15744-434: Was the destruction of the oil refinery at Vallø (Tønsberg) in southern Norway by 107 Lancasters, on the night of 25/26 April 1945. Once the surrender of Germany had occurred, plans were made to send a "Very Long Range Bomber Force" known as Tiger Force to participate in the Pacific war against Japan. Made up of about 30 British Commonwealth heavy bomber squadrons, a reduction of the original plan of about 1,000 aircraft,

15872-406: Was the use of a range of increasingly sophisticated electronic aids to navigation and the other was the use of specialist Pathfinders . The technical aids to navigation took two forms. One was external radio navigation aids, as exemplified by Gee and the later highly accurate Oboe systems. The other was the centimetric navigation equipment H2S radar carried in the bombers. The Pathfinders were

16000-438: Was to restrict bombing to military targets and infrastructure , such as ports and railways which were of military importance. While acknowledging that bombing Germany would cause civilian casualties, the British government renounced deliberate bombing of civilian property (outside combat zones) as a military tactic. The British government did not want to violate its agreement by attacking civilian targets outside combat zones and

16128-464: Was unveiled by Queen Elizabeth II on 28 June 2012 to commemorate the high casualty rate among the aircrews. In April 2018 The International Bomber Command Centre was opened in Lincoln. At the time of the formation of Bomber Command in 1936, Giulio Douhet 's slogan " the bomber will always get through " was popular, and figures like Stanley Baldwin cited it. Until advances in radar technology in

16256-404: Was used to trigger the display sweep. When first activated, it would be unlikely to have exactly the same timing as the master station, so the operator would see the pattern of blips traveling across the screen. A control knob that adjusted the oscillator was used to tune the local oscillator frequency until the blips on the display were stationary which meant the local and master oscillators now had

16384-430: Was usually a Dornier Do 17 Z-10, Junkers Ju 88 C or Messerschmitt Bf 110 . This technique of ground-controlled interception (GCI) was preceded by the use of single-engined non radar-equipped Bf 109s guided to the attacking bombers by the illumination of searchlights , termed; Helle Nachtjagd – illuminated night fighting. RAF bombers flying into Germany or France had to cross the line at some point, at which time

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