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113-741: The United States reverse-engineered the design for the Ford PJ31 powering the Republic-Ford JB-2 cruise missile and the experimental USAAF -developed JB-4 television-guided bomb. The origins of the Argus As 014 lie in 1928, when Munich inventor Paul Schmidt began work on a new design of pulse jet engine. Schmidt received a patent on his design in 1931 and received support from the German Air Ministry in 1933. In 1934, along with Professor Georg Madelung , Schmidt proposed

226-457: A "dump" command sent to the missile or by one sent from the air log propeller. The Navy program lasted until the last launch of a LTV-N-2 on September 11, 1953. The LTV-N-2 program developed a number of launchers and varied launching techniques, variations in guidance, command guidance computers, the TROUNCE guidances system for SSM-N-8 Regulus , telemetry systems, flight termination, and tested

339-652: A "flying bomb" to be powered by his pulse jet to the Ministry and received a development contract the following year. In 1938 he demonstrated a pulse jet–powered pilotless bomber, but the project was shelved by the Air Ministry as the prototype lacked range and accuracy and was expensive to construct. That same year, however, the Argus Company began work on a flying bomb using Schmidt's engine. Schmidt later joined Argus in 1940. A model of simplicity and low cost,

452-606: A 30 feet (9.1 m) long wooden ramp JB-2 testing at Eglin the Santa Rosa Island Range Complex , Area A-10 began in March 1947. The first launcher to be used was 8OK248. The first launch was from a 50 feet (15 m) mobile ramp quite different from the fixed long J ramps used by the Germans. 8OK248, was a mobile launcher site which emphasizes how quickly US practice had diverged from German practice in

565-604: A J30 turbojet as a power plant. The operational reliability of the LTV-N-2 was calculated to be 61.8% but in practice turned out to be only 55.9% The Navy concluded that the reliability of the Loon could not be significantly altered as "improved techniques have just kept pace with component deterioration." The missiles all were manufactured in 1945-46 and were getting old. After the United States Air Force became

678-464: A V-1 carried no coils or magnetos to power the spark plug once launched. Since the engine was rather simple, low-grade gasoline could be used and a good amount of thrust — 2.7 kN (660 lb f ) — was produced, but it was inefficient, limiting the range of the V-1 to 240–400 km (150–250 mi) The resonant frequency of this combustion process was around 45 Hz, giving

791-489: A debate developed" amongst Western Allied political and military leaders, "over the size, mission, equipment, and support of these contingents". Following negotiations, it was decided that Coronet would include a joint Commonwealth Corps , made up of infantry divisions from the Australian, New Zealand , British and Canadian armies. Reinforcements would have been available from those countries, as well as other parts of

904-558: A flying-wing aircraft with two General Electric B1 turbojets in the center section, and two 900 kg (2000 lb) general-purpose bombs in enclosed "bomb containers" in the wing roots. To test the aerodynamics of the design, one JB-1 was completed as a manned unpowered glider, which was first flown in August 1944. Motivated by intelligence information supplied by the United Kingdom , Project MX-544 to create an American copy of

1017-727: A force of 500–1,000 aircraft, including units dedicated to aerial refueling . Planning was later scaled back to 22 squadrons and, by the time the war ended, to 10 squadrons: between 120 and 150 Avro Lancasters / Lincolns , operating out of airbases on Okinawa. Tiger Force was to have included the elite 617 Squadron , also known as "The Dambusters", which carried out specialist bombing operations. Initially, US planners also did not plan to use any non-US Allied ground forces in Operation Downfall. Had reinforcements been needed at an early stage of Olympic, they would have been diverted from US forces being assembled for Coronet—for which there

1130-806: A fully functional As 014 on a test stand. Republic-Ford JB-2 The Republic-Ford JB-2 , also known as the Thunderbug , KGW and LTV-N-2 Loon , was an American copy of the German V-1 flying bomb . Developed in 1944, and planned to be used in the Allied invasion of Japan ( Operation Downfall ), the JB-2 was never used in combat. It was the most successful of the United States Army Air Forces Jet Bomb (JB) projects (JB-1 through JB-10) during World War II . Postwar,

1243-572: A fully independent arm of the National Military Establishment 18 September 1947, research continued with the development of unmanned aircraft and pilotless bombers, including the already available JB-2. The USAF Air Materiel Command reactivated the JB-2 as Project EO-727-12 on 23 April 1948, at Holloman Air Force Base , New Mexico. The JB-2 was used for development of missile guidance control and seeker systems, testing of telemetering and optical tracking facilities, and as

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1356-761: A joint Canadian–British–American planning team had produced a plan ("Appreciation and Plan for the Defeat of Japan") which did not call for an invasion of the Japanese Home Islands until 1947–48. The American Joint Chiefs of Staff believed that prolonging the war to such an extent was dangerous for national morale. Instead, at the Quebec conference, the Combined Chiefs of Staff agreed that Japan should be forced to surrender not more than one year after Germany's surrender . The United States Navy urged

1469-541: A realistic prospect of winning the war, Japan's leaders believed they could make the cost of invading and occupying the Home Islands too high for the Allies to accept, which would lead to some sort of armistice rather than total defeat. The Japanese plan for defeating the invasion was called Operation Ketsugō (ja) ( 決号作戦 , ketsugō sakusen ) ("Operation: Decisive" or "Final Battle"). The Japanese planned to commit

1582-729: A reproduction of an As 014. The engine was demonstrated at the 2010 show. The V-1 flying bomb held by the London Science Museum features a sectioned As 014 engine. Other museums displaying V-1s complete with their engines include the Imperial War Museum Duxford , Royal Air Force Museum Cosford , the Royal Air Force Museum London and the Military Aviation Museum . The Military Aviation Museum also features

1695-619: A series of tests in the late 1940s at Eglin Air Corps Proving Ground Eglin Air Force Base , Florida. In early 1949, the 3200th Proof Test Group tested launching JB-2s from the under the wings of B-36 Peacemaker bombers at Eglin AFB. About a year later, JB-2s were tested as aerial targets for experimental infrared gunsights at Eglin. The Navy version was featured in the movie The Flying Missile (1951), including submarine launches. The movie shows

1808-490: A similar number wounded per sortie —and Kyūshū was likely to be worse. To attack the ships off Okinawa, Japanese planes had to fly long distances over open water; to attack the ships off Kyūshū, they could fly overland and then short distances out to the landing fleets. Gradually, intelligence learned that the Japanese were devoting all their aircraft to the kamikaze mission and taking effective measures to conserve them until

1921-508: A staging ground and a valuable airbase for Operation Coronet. After the name Operation Olympic was compromised by being sent out in unsecured code, the name Operation Majestic was adopted. Operation Coronet, the invasion of Honshu at the Kantō Plain south of the capital, was to begin on "Y-Day", which was tentatively scheduled for March 1, 1946. Coronet would have been even larger than Olympic, with up to 45 U.S. divisions assigned for both

2034-739: A stretch of Santa Rosa Island was purchased by the USAAF for the launch of guided missiles. The replacement launch site was located 22 miles further west on Santa Rosa island from Range 64. Following the war the 1st Experimental Guided Missiles Group was created in January 1946 to replace the ad hoc units which had been at Range 64. The Eglin JB-2 launch sites were located in Area A-10 of Eglin AFB. The Area-10 JB-2 launch sites on Santa Rosa Island are now designated as archeological sites 8OK246 (30°23’57”N 086°42’19”W) and 8OK248 (30°23’54”N 086°41’33”W) which

2147-548: A target for new surface-to-air and air-to-air missiles (fulfilling the V1's cover name, Flakzielgerät  — anti-aircraft target device). The JB-2 project used the North American Aviation NATIV (North American Test Instrument Vehicle) Blockhouse and two launch ramps at Holloman: a 400 ft (120 m), two-rail ramp on a 3° earth-filled slope, and a 40 ft (12 m) trailer ramp. The trailer ramp

2260-580: A total of 900,000 men. Although the Japanese were able to muster new soldiers, equipping them was more difficult. By August, the Japanese Army had the equivalent of 65 divisions in the homeland but only enough equipment for 40 and ammunition for 30. The Japanese did not formally decide to stake everything on the outcome of the Battle of Kyūshū, but they concentrated their assets to such a degree that there would be little left in reserve. By one estimate,

2373-696: The Mariana Islands . Following the end of the war in Europe in May 1945, plans were also made to transfer some of the heavy bomber groups of the veteran Eighth Air Force to airbases on Okinawa to conduct strategic bombing raids in coordination with the Twentieth. The Eighth was to upgrade their B-17 Flying Fortresses and B-24 Liberators to B-29 Superfortresses (the group received its first B-29 on August 8, 1945). In total, General Henry Arnold estimated that

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2486-473: The New Guinea and Borneo campaigns , should be appointed. The war ended before the details of the corps were finalized. Figures for Coronet exclude values for both the immediate strategic reserve of 3 divisions as well as the 17 division strategic reserve in the U.S. and any British/Commonwealth forces. Meanwhile, the Japanese had their own plans. Initially, they were concerned about an invasion during

2599-532: The U.S. Army Air Forces ). At the time, the development of the atomic bomb was a very closely guarded secret (not even then-Vice President Harry Truman knew of its existence until he became president), known only to a few top officials outside the Manhattan Project (and to the Soviet espionage apparatus, which had managed to infiltrate agents into, or recruit agents from within the program, despite

2712-682: The United States Strategic Air Forces in the Pacific (USASTAF)—a formation which comprised the Eighth and Twentieth air forces, as well as the British Tiger Force . USASTAF and Tiger Force were to remain active through Operation Coronet. The Twentieth Air Force was to have continued its role as the main Allied strategic bomber force used against the Japanese home islands, operating from airfields in

2825-481: The abdomen ." They were expected to serve as a "second defense line" during the Allied invasion, and to conduct guerrilla warfare in urban areas and mountains. The Japanese command intended to organize its Army personnel according to the following plan: US military intelligence initially estimated the number of Japanese aircraft to be around 2,500. The Okinawa experience was bad for the US—almost two fatalities and

2938-523: The Army Air Forces had JB-2 crews on transports headed for use against Japan. The war's end led to the cancellation of Operation Downfall and the production of JB-2s was terminated on 15 September. A total of 1,391 were manufactured. Though production was halted in mid-September 1945 testing was continued with JB-2s already constructed. Planning for the post war development of Guided Missiles at Eglin had begun prior to VJ Day. On August 13, 1945

3051-628: The Chinese coast, and in the Yellow Sea area. Tactical air support was to be the responsibility of the Fifth , Seventh , and Thirteenth Air Forces . These were responsible for attacking Japanese airfields and transportation arteries on Kyushu and Southern Honshu (e.g. the Kanmon Tunnel ) and for gaining and maintaining air superiority over the beaches. The task of strategic bombing fell on

3164-655: The Commonwealth Corps, a combined Commonwealth fleet should be led by Vice-Admiral Sir William Tennant , and that—as Commonwealth air units would be dominated by the RAAF – the Air Officer Commanding should be Australian. However, the Australian government questioned the appointment of an officer with no experience in fighting the Japanese, such as Keightley and suggested that Lieutenant General Leslie Morshead , an Australian who had been carrying out

3277-572: The Commonwealth. However, MacArthur blocked proposals to include an Indian Army division because of differences in language, organization, composition, equipment, training and doctrine. He also recommended that the corps be organized along the lines of a U.S. corps, should use only U.S. equipment and logistics, and should train in the U.S. for six months before deployment; these suggestions were accepted. The British Government suggested that: Lieutenant-General Sir Charles Keightley should command

3390-660: The Ford copy of the Argus pulse-jet engine of the JB-2 was much less than the GE turbojets. Subsequently, work proceeded on the JB-2 for final development and production. An initial production order was 1,000 units, with subsequent production of 1,000 per month. That figure was not anticipated to be attainable until April 1945. Republic had its production lines at capacity for producing P-47 Thunderbolts , so it sub-contracted airframe manufacturing to Willys-Overland . Ford Motor Company built

3503-474: The IJN still maintained a fleet of thousands of warplanes and possessed nearly 2 million personnel in the Home Islands, ensuring it a large role in the coming defensive operation. In addition, Japan had about 100 Kōryū -class midget submarines , 300 smaller Kairyū -class midget submarines, 120 Kaiten manned torpedoes , and 2,412 Shin'yō suicide motorboats. Unlike the larger ships, these, together with

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3616-413: The JB-2 and the V-1 was the shape of the forward pulsejet support pylon — the original V-1 had its support pylon slightly swept back at nearly the same angle on both its leading and trailing edges, while the JB-2's pylon had a vertical leading edge and sharply swept-forward trailing edge. A similar, completely coincidental re-shaping, but with a much broader chord, was used for the same airframe component of

3729-486: The JB-2 began in 1945. By April the Aircraft Radio Laboratory at Wright Field had developed a radio/radar control system utilizing the highly accurate SCR-584 radar unit to track a AN/APW-1 radar transceiver equipped JB-2. A SCR-584 tracked the missile's transceiver and sent control signals to correct the missile's course. With the new guidance system the JB-2 became a much more advanced missile than

3842-598: The JB-2 played a significant role in the development of more advanced surface-to-surface tactical missile systems such as the MGM-1 Matador and later MGM-13 Mace . The United States had known of the existence of a new German secret weapon since 22 August 1942 when a Danish naval officer discovered an early test version of the V-1 that had crashed on the island of Bornholm , in the Baltic Sea between Germany and Sweden, roughly 120 kilometers (75 miles) northeast of

3955-538: The JB-2. The matter of guided missiles became a jurisdictional issue between Army ground Forces and the Army Air Forces. The dispute was decided in favor of the AAF as the JB-2 had wings and flew. It was decided that the JB-2 "should be placed in combat, needed or not, as an insurance measure for AAF claims. By 8 September, the first of thirteen complete JB-2s, reverse engineered from the material received at Wright Field in July

4068-598: The JB-2. Ultimately nine launch ramps of varying length and method of propulsion were built at Range 64. While copying the V-1 proved easy, inventing a means of launching proved very difficult. The first launch of a JB-2 from Range 64 was on October 12, 1944 by the 1st Proving Ground Group . A total of 233 JB-2s were launched from Range 64 between October 1944 and October 1945. All further tests at Range 64 were cancelled in November 1945 and orders were issued to deconstruct, remove or abandon everything by December 12, 1945. After

4181-603: The Japanese military in the Home Islands amounted to 4,335,500, of whom 2,372,700 were in the Army and 1,962,800 in the Navy. The buildup of Japanese troops on Kyūshū led American war planners, most importantly General George Marshall, to consider drastic changes to Olympic, or replacing it with a different invasion plan. Fears of "an Okinawa from one end of Japan to the other" encouraged the Allies to consider unconventional weapons, including chemical warfare. Widespread chemical warfare

4294-634: The Navy in 1948. In 1947 the USAF decided to move JB-2 testing to Alamogordo Air Force Base , New Mexico using the test range at White Sands. The U.S. Navy's version, the KGW-1 was intended for installation on surface ships and shore installations. In 1946 it was re-designated KUW as a test vehicle, then renamed LTV-N-2. The first launch of a LTV-N-2 was from Point Mugu , California on January 7, 1946. The initial land based launch facilities at Point Mugu closely resembled those at area A-10 at Eglin AAF. Later

4407-476: The Navy's losses at Okinawa. Allied counter- kamikaze preparations were known as the Big Blue Blanket . This involved adding more fighter squadrons to the carriers in place of torpedo and dive bombers , and converting B-17s into airborne radar pickets in a manner similar to present-day AWACS . Nimitz planned a pre-invasion feint, sending a fleet to the invasion beaches a couple of weeks before

4520-634: The US inventory and as such was used for much experimentation. Later tests included determining how long it took an experienced crew to prepare and launch a missile. Up to 30 missiles were launched by a single crew in a day. Tests with the JB-2 at Eglin continued until the summer of 1950 when the Korean War changed the priorities of the USAF and US Navy. The JB-2 was designated the LTV-1 in late 1947, then LTV-A-1 (from "Launch test vehicle, Air Force 1") and LTV-N-2 by

4633-482: The V-1 its nicknames "buzz bomb" or "doodlebug", because of the sputtering sound it emitted. The prototype engine was tested while slung below a Gotha Go 145 Luftwaffe training biplane marked D-IIWS in April 1941 and the first prototype V-1 flew on December 24 of 1942. The As 014, as well as the higher thrust As 044 pulsejet engine, was also under consideration as a power source for various last-ditch German fighters in

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4746-555: The V-1 test launch ramp at the Peenemünde Army Research Center , on Germany's Usedom Island . A photograph and a detailed sketch of the V-1 test unit, the Fieseler Fi 103 V83 ( Versuchs -83, the eighty-third prototype airframe) was sent to Britain. This led to months of intelligence-gathering and intelligence-sifting which traced the weapon to the airfield at Peenemünde , on Germany's Baltic Coast,

4859-556: The V-1 was initiated. In July 1944, three weeks after German V-1 "Buzz Bombs" first struck England on 12 and 13 June, American engineers at Wright Field fired a working copy of the German Argus As 014 pulse-jet engine, "reverse-engineered" from crashed German V-1s that were brought to the United States from England for analysis. The reverse engineering provided the design of America's first mass-produced guided missile,

4972-399: The V-1 was stationary on its launch ramp after reaching minimum operating temperature. Ignition was initiated by an automotive-type spark plug located about 0.75 m (2 ft 6 in) behind the shutter system, electricity to the plug being supplied from a portable starting unit. Three air nozzles in the front of the pulse jet were connected to an external high pressure air source which

5085-458: The V-1. At one point proponents envisioned 75,000 JB-2s planned for production. This was absurd as it would have competed with the established manned bomber forces for sealift from America to Europe. It was estimated that the presumed launch rate of JB-2s would consume 25% of available shipping. Commander of Strategic Air Forces in Europe, Spaatz proposed a much more limited role as a harassment weapon on days where weather limited bombers. Moreover

5198-546: The air forces only wanted the JB-2 if it caused no curtailment of the supply of bombs, artillery shells, and personnel being shipped to Europe. A USAAF launching squadron was formed in anticipation for using the weapons both against Nazi Germany and Japan. The motive for this rush to deploy the JB-2 was the struggle for control of guided missiles between the Army Air Force and the Army Ground Forces. This

5311-466: The battle. An Army estimate in May was 3,391 planes; in June, 4,862; in August, 5,911. A July Navy estimate, abandoning any distinction between training and combat aircraft, was 8,750; in August, 10,290. By the time the war ended, the Japanese actually possessed some 12,700 aircraft in the Home Islands, roughly half kamikazes . Ketsu plans for Kyushu envisioned committing nearly 9,000 aircraft according to

5424-511: The beaches of the Kantō Plain (both southwest and southeast of Tokyo ) were realistic invasion zones. The Allies decided to launch a two-stage invasion. Operation Olympic would attack southern Kyūshū. Airbases would be established, which would give cover for Operation Coronet, the attack on Tokyo Bay . While the geography of Japan was known, the U.S. military planners had to estimate the defending forces that they would face. Based on intelligence available early in 1945, their assumptions included

5537-589: The bomb tonnage dropped in the Pacific Theater by USAAF aircraft alone would exceed 1,050,000 tons in 1945 and 3,150,000 tons in 1946, excluding the blast yields of nuclear weapons. Before the main invasion, the offshore islands of Tanegashima , Yakushima , and the Koshikijima Islands were to be taken, starting on X−5. The invasion of Okinawa had demonstrated the value of establishing secure anchorages close at hand, for ships not needed off

5650-689: The closing days of World War II. Production totaled 31,100 units. After the Second World War the As 014 was reverse-engineered / copied for use by the United States as the Ford PJ31 on the Republic-Ford JB-2 ( Fieseler Fi 103 copy), and by the Soviet Union as the Chelomey D-3 on the 10Kh (also a Fieseler Fi 103 copy). The Planes of Fame Air Museum in Chino, California , constructed

5763-670: The combat effectiveness of many units. The Australian government had asked at an early stage for the inclusion of an Australian Army infantry division in the first wave (Olympic). This was rejected by U.S. commanders and even the initial plans for Coronet, according to U.S. historian John Ray Skates, did not envisage that units from Commonwealth or other Allied armies would be landed on the Kantō Plain in 1946. The first official "plans indicated that assault, followup, and reserve units would all come from US forces". By mid-1945—when plans for Coronet were being reworked—many other Allied countries had, according to Skates, "offered ground forces, and

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5876-438: The destroyers and fleet submarines, were expected to see extensive action defending the shores, with a view to destroying about 60 Allied transports. The Navy trained a unit of frogmen to serve as suicide bombers, the Fukuryu . They were to be armed with contact-fuzed mines , and to dive under landing craft and blow them up. An inventory of mines was anchored to the sea bottom off each potential invasion beach for their use by

5989-399: The development of the JB-2. The launch site was designated L-1. The other launcher, 8OK246, was a fixed launcher with a track 400 feet (120 m) long. Competitive testing of 179 ramp launched and 107 air launched JB-2s using both the pre-set mechanical system vs the radio/radar control system was the first major effort at Eglin. The JB-2 was essentially the only operational guided missile in

6102-421: The direction of a distant mountain range where their destruction by ground impact was assured. The launch area is visible in aerial imagery ( 40°41′53″N 114°02′29″W  /  40.69806°N 114.04139°W  / 40.69806; -114.04139 ). Parts of crashed JB-2s are occasionally found by Wendover Airport personnel. In December 1944, the first JB-1 was ready for launch from Range 64. The missile

6215-433: The engine was made from a sheet of mild steel rolled into a tube. At the front of the engine there was a spring flap-valve grid (shutters), a fuel inlet valve and an igniter. It could run on any grade of petroleum fuel and its shutter system was not expected to last longer than one flight, as it had an operational life of approximately one hour. The engine was a resonant jet which, contrary to popular legend, could operate while

6328-465: The engine, initially designated IJ-15-1, which was a copy of the V-1's 900-lb. thrust Argus-Schmidt pulse-jet (the Argus As 014 ), later designated the PJ31 . Guidance and flight controls were manufactured by Jack and Heintz Company of Cleveland , Ohio, and Monsanto took on the task of designing a better launching system, with Northrop supplying the launch sleds. Production delivery began in January 1945. Development of an improved guidance method for

6441-420: The entire population of Japan to resisting the invasion, and from June 1945 onward, a propaganda campaign calling for "The Glorious Death of One Hundred Million" commenced. The main message of "The Glorious Death of One Hundred Million" campaign was that it was "glorious to die for the holy emperor of Japan, and every Japanese man, woman, and child should die for the Emperor when the Allies arrived". Although it

6554-530: The facilities at Point Mugu were expanded to include the XM1 launch ramp and the Rolling Ramp which designed to provide rolling movements to simulate launching from a ship. As KUW/LTV-N-2 and given the name of an aquatic bird the "Loon" it was developed to be carried on the aft deck of submarines in watertight containers. The submarine to carry the LTV-N-2 was USS  Cusk  (SS-348) which successfully launched its first Loon on 12 February 1947, off Point Mugu, CA. The submarine USS  Carbonero  (SS-337)

6667-400: The fire-bombing campaign against Japanese cities and the blockade of food and supplies until the Japanese surrendered. However, General Marshall argued that forcing surrender that way might take several years, if ever. Accordingly, Marshall and United States Secretary of the Navy Frank Knox concluded the Americans would have to invade Japan to end the war, regardless of casualties. Despite

6780-716: The first attempts at a powered cruise missile for potential usage in America's arsenal. Early launches of JB-1, JB-2, and JB-10 missiles were from a site along the coast on Santa Rosa Island in what is now Sandestin, Florida. The land necessary was leased at $ 1 a year for the duration of the war. The test location was 22 miles (35 km) east of Eglin Army Air Field designated Range 64 (aka C-64) 30°12′9″N 085°50′59″W  /  30.20250°N 85.84972°W  / 30.20250; -85.84972  ( Range 64 ) ( 30°23′54″N 086°41′33″W  /  30.39833°N 86.69250°W  / 30.39833; -86.69250 ) and involved 2 + 1 ⁄ 2 miles (4.0 km) of

6893-464: The first launch at the new facility was caused by staffing requirements, the logistics chain and construction delays. During the war things could be done in a hurry. After the war hurry up became wait. While the unit waited for the opening of the facilities on Santa Rosa Island to be constructed the First Experimental Guided Missile Group was conducting cold weather testing at Ladd Field, Alaska, in Project Frigid. At Ladd they successfully launched JB-2s off

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7006-485: The following sequence: The Japanese planned to commit the majority of their air forces to action within 10 days after the Allied fleet's arrival off Kyūshū. They hoped that at least 15 to 20% (or even up to a half) of the US transport ships would be destroyed before disembarkation. The United States Strategic Bombing Survey subsequently estimated that if the Japanese managed 5,000 kamikaze sorties, they could have sunk around 90 ships and damaged another 900, roughly triple

7119-418: The following: Operation Olympic, the invasion of Kyūshū, was to begin on "X-Day", which was scheduled for November 1, 1945. The combined Allied naval armada would have been the largest ever assembled, including 42 aircraft carriers , 24 battleships , and 400 destroyers and destroyer escorts . Fourteen U.S. divisions and a "division-equivalent" (two regimental combat teams ) were scheduled to take part in

7232-713: The forces in Kyūshū had 40% of all the ammunition in the Home Islands. In addition, the Japanese had organized the Volunteer Fighting Corps , which included all healthy men aged 15 to 60 and women 17 to 40 for a total of 28 million people, for combat support and, later, combat jobs. Weapons, training and uniforms were generally lacking: many were armed with nothing better than antiquated firearms, molotov cocktails , longbows , swords, knives, bamboo or wooden spears, and even clubs and truncheons: they were expected to make do with what they had. One mobilized high school girl, Yukiko Kasai, found herself issued an awl and told, "Even killing one American soldier will do. ... You must aim for

7345-412: The ground would require their deployment after landings had been accomplished. Deployment from B-29s would take too long to modify the B-29s necessary. A navalized version, designated KGW-1 , was planned to be used against Japan from LSTs ( Landing Ship, Tank ) as well as escort carriers (CVEs). In addition, launches from PB4Y-2 Privateers were foreseen and techniques developed. As WWII ended in Europe

7458-412: The impressment of wood and fabric airframe training aircraft into the kamikaze role which would have been difficult for Allied radar systems of the time to detect and track), they hoped to raise that to one for six by overwhelming the US defenses with large numbers of kamikaze attacks within a period of hours. The Japanese estimated that the planes would sink more than 400 ships; since they were training

7571-638: The initial landing and follow-up (The Overlord invasion of Normandy , by comparison, deployed 12 divisions in the initial landings.). In the initial stage, the First Army would have invaded at Kujūkuri Beach , on the Bōsō Peninsula , while the Eighth Army invaded at Hiratsuka , on Sagami Bay ; these armies would have comprised 25 divisions between them. Later, a follow-up force of up to 20 additional U.S. divisions and up to 5 or more British Commonwealth divisions would have landed as reinforcements. The Allied forces would then have driven north and inland, encircling Tokyo and pressing on toward Nagano. Olympic

7684-533: The initial landings. Using Okinawa as a staging base, the objective would have been to seize the southern portion of Kyūshū. This area would then be used as a further staging point to attack Honshu in Operation Coronet. Olympic was also to include a deception plan, known as Operation Pastel . Pastel was designed to convince the Japanese that the Joint Chiefs had rejected the notion of a direct invasion and instead were going to attempt to encircle and bombard Japan. This would require capturing bases in Formosa , along

7797-430: The invasion planners assumed that the Americans would outnumber the Japanese by roughly three to one. In early 1945, Miyazaki was virtually undefended, while Ariake, with its good nearby harbor, was heavily defended. The invasion was not intended to conquer the entire island, just the southernmost third of it, as indicated by the dashed line on the map labeled "general limit of northern advance". Southern Kyūshū would offer

7910-473: The invasion, and air strength had been increasing in preparation for the all-out assault on Japan. In preparation for the invasion, an air campaign against Japanese airfields and transportation arteries had commenced before the Japanese surrender. Through April, May, and June, Allied intelligence followed the buildup of Japanese ground forces, including five divisions added to Kyūshū, with great interest, but also some complacency, still projecting that in November

8023-456: The island’s shore line as well as extending 150 miles (240 km) off shore. Range 64 was a self-sufficient facility with not only launch and missile preparation facilities, but included barracks, mess hall and administrative facilities as well. Later a Training Unit P had to be located 1 + 1 ⁄ 2 miles (2.4 km) east of Range 64 to house men developing the techniques needed for field operations in combat while being trained to field

8136-551: The landing beaches and for ships damaged by air attack. Kyūshū was to be invaded by the Sixth United States Army at three points: Miyazaki , Ariake , and Kushikino . If a clock were drawn on a map of Kyūshū, these points would roughly correspond to 4, 5, and 7 o'clock, respectively. The 35 landing beaches were all named for automobiles: Austin , Buick , Cadillac , and so on through to Stutz , Winton , and Zephyr . With one corps assigned to each landing,

8249-470: The largest amphibious operation in history, surpassing D-Day . Japan's geography made this invasion plan obvious to the Japanese as well; they were able to accurately predict the Allied invasion plans and thus adjust their defensive plan, Operation Ketsugō (ja) , accordingly. The Japanese planned an all-out defense of Kyūshū, with little left in reserve for any subsequent defense operations. Casualty predictions varied widely, but were extremely high: into

8362-654: The largest landing. In March 1945, there was only one combat division in Kyūshū. Four veteran divisions were withdrawn from the Kwantung Army in Manchuria in March 1945 to strengthen the forces in Japan, and 45 new divisions were activated between February and May 1945. Most were immobile formations for coastal defense, but 16 were high quality mobile divisions. By August, the formations, including three tank brigades, had

8475-404: The manned Fieseler Fi 103R Reichenberg , original V-1 ordnance development. Initial testing of the first batch of prototype missiles resulted in a decision to change from the preset guidance of the V-1 to a command guidance system utilizing a radar beacon in the missile and radio command guidance from a tracking SCR-584 radar. With its Ford-produced PJ31 pulsejet powerplant, the JB-2 was one of

8588-622: The millions, depending on the extent of resistance by Japanese civilians. Responsibility for the planning of Operation Downfall fell to American commanders Fleet Admiral Chester Nimitz , General of the Army Douglas MacArthur and the Joint Chiefs of Staff —Fleet Admirals Ernest King and William D. Leahy , and Generals of the Army George Marshall and Hap Arnold (the latter being the commander of

8701-668: The missile being launched from a trolley with four JATO bottles. In the mid-1992, military crews uncovered the well-preserved wreckage of a JB-2 at a site on an Air Force-owned section of Santa Rosa Island . Most crash sites on the barrier island were little more than flaky rust, but after the find, officials were planning further searches. Related development Aircraft of comparable role, configuration, and era Launch locations [REDACTED]  This article incorporates public domain material from the Air Force Historical Research Agency Operation Downfall Second Sino-Japanese War Operation Downfall

8814-431: The mission. More than 10,000 aircraft were ready for use in July (with more by October), as well as hundreds of newly built small suicide boats to attack Allied ships offshore. Up to 2,000 kamikaze planes launched attacks during the Battle of Okinawa, achieving approximately one hit per nine attacks. At Kyūshū, because of the more favorable circumstances (such as terrain that would reduce the Allies' radar advantage, and

8927-462: The most defensible terrain. For the defense of Kyūshū, the Japanese took an intermediate posture, with the bulk of their defensive forces a few kilometers inland, back far enough to avoid complete exposure to naval bombardment, but close enough that the Americans could not establish a secure foothold before engaging them. The counteroffensive forces were still farther back, prepared to move against

9040-466: The pilots to target transports rather than carriers and destroyers, the casualties would be disproportionately greater than at Okinawa. One staff study estimated that the kamikazes could destroy a third to half of the invasion force before landing. Admiral King, Commander-in-Chief of the U.S. Navy, was so concerned about losses from kamikaze attacks that he and other senior naval officers argued for canceling Operation Downfall and for instead continuing

9153-458: The potential to deploy ten. "These [six] divisions have since made their appearance, as predicted," he observed, "and the end is not in sight." If not checked, this threatened "to grow to [the] point where we attack on a ratio of one (1) to one (1) which is not the recipe for victory." By the time of surrender, the Japanese had over 735,000 military personnel either in position or in various stages of deployment on Kyushu alone. The total strength of

9266-407: The pulse jet firing. Each cycle or pulse of the engine began with the shutters open; fuel was injected behind them and ignited, and the resulting expansion of gases forced the shutters closed. As the pressure in the engine dropped following combustion, the shutters reopened and the cycle was repeated, roughly 45 to 55 times per second. The electrical ignition system was needed only to start the engine -

9379-488: The real invasion, to lure out the Japanese on their one-way flights, who would then find ships bristling with anti-aircraft guns instead of the valuable, vulnerable transports. The main defense against Japanese air attacks would have come from the massive fighter forces being assembled in the Ryukyu Islands . The US Army Fifth and Seventh Air Forces and US Marine air units had moved into the islands immediately after

9492-641: The same orders would have been given in the home islands. The Japanese were secretly constructing an underground headquarters in Matsushiro, Nagano Prefecture, to shelter the Emperor and the Imperial General Staff during an invasion. In planning for Operation Ketsugo, IGHQ overestimated the strength of the invading forces: while the Allied invasion plan called for fewer than 70 divisions, the Japanese expected up to 90. Admiral Matome Ugaki

9605-752: The shattering damage it had absorbed by this stage of the war, the Imperial Japanese Navy , by then organized under the Navy General Command, was determined to inflict as much damage on the Allies as possible. Remaining major warships numbered four battleships (all damaged), five damaged aircraft carriers, two cruisers, 23 destroyers, and 46 submarines. However, the IJN lacked enough fuel for further sorties by its capital ships and planned instead to use its anti-aircraft firepower to defend naval installations while docked in port. Despite its inability to conduct large-scale fleet operations,

9718-512: The strategic use of chemical weapons on a massive scale was not seriously studied or proposed by any senior American leader; rather, they debated the tactical use of chemical weapons against pockets of Japanese resistance. Although chemical warfare had been outlawed by the Geneva Protocol , neither the United States nor Japan was a signatory at the time. While the US had promised never to initiate gas warfare, Japan had used gas against

9831-542: The suicide divers, with up to 10,000 mines planned. Some 1,200 suicide divers had been trained before the Japanese surrender. The two defensive options against amphibious invasion are strong defense of the beaches and defense in depth . Early in the war (such as at Tarawa ), the Japanese employed strong defenses on the beaches with little or no manpower in reserve, but this tactic proved vulnerable to pre-invasion shore bombardment . Later at Peleliu , Iwo Jima , and Okinawa, they switched strategies and dug in their forces in

9944-553: The summer of 1945. However, the Battle of Okinawa went on for so long that they concluded the Allies would not be able to launch another operation before the typhoon season , during which the weather would be too risky for amphibious operations. Japanese intelligence predicted fairly closely where the invasion would take place: southern Kyūshū at Miyazaki, Ariake Bay and/or the Satsuma Peninsula . While Japan no longer had

10057-437: The tight security around it), and the initial planning for the invasion of Japan did not take its existence into consideration. Once the atomic bomb became available, General Marshall envisioned using it to support the invasion if sufficient numbers could be produced in time. The Pacific War was not under a single Allied commander-in-chief (C-in-C). Allied command was divided into regions: by 1945, for example, Chester Nimitz

10170-463: The top-secret German missile test and development site. As more intelligence data was obtained through aerial photography and sources inside Germany, the United States decided to develop a jet-powered flying bomb in 1943. The United States Army Air Forces gave Northrop Aircraft a contract in July 1944 to develop the JB-1 (Jet Bomb 1) turbojet-powered flying bomb under project MX-543. Northrop designed

10283-406: The total for Kyūshū would be about 350,000 servicemen. That changed in July, with the discovery of four new divisions and indications of more to come. By August, the count was up to 600,000, and Magic cryptanalysis had identified nine divisions in southern Kyūshū—three times the expected number and still a serious underestimate of the actual Japanese strength. Estimated troop strength in early July

10396-526: The use of a blockade and airpower to bring about Japan's capitulation. They proposed operations to capture airbases in nearby Shanghai , China , and Korea , which would give the United States Army Air Forces a series of forward airbases from which to bombard Japan into submission. The Army, on the other hand, argued that such a strategy could "prolong the war indefinitely" and expend lives needlessly, and therefore that an invasion

10509-764: The war ended the land leased for a single dollar was returned to the Coffeen family. The site of Range 64 is now the Coffeen Nature Preserve, Four Mile Village and Topsail Hill Preserve State Park in Sandestin, FL. As the Heinkel He 111H-22 had done late in the war for the Luftwaffe in offensive air-launches of V-1s against the Allies , JB-2s were launched from MB-17G 44-85815 based at Hurlburt Field beginning in early 1945 and continued after

10622-478: The war ended. In addition to Range 64, a detachment of the Special Weapons Branch, Wright Field, Ohio, arrived at Wendover Field , Utah , in 1944 with the mission of evaluating captured and experimental systems, including the JB-2. Testing was from a launch structure just south of Wendover's technical site. Unlike the missiles fired at Range 64 the ones fired at Wendover were armed and fired in

10735-475: Was 350,000, rising to 545,000 in early August. The intelligence revelations about Japanese preparations on Kyushu emerging in mid-July transmitted powerful shock waves both in the Pacific and in Washington. On 29 July, MacArthur's intelligence chief, Major General Charles A. Willoughby , was the first to note that the April estimate allowed for the Japanese capability to deploy six divisions on Kyushu, with

10848-567: Was about 0.5 miles (800 m) away from 8OK246. Launches from the Boeing B-17G , Boeing B-29 , and B-36 Peacemaker bombers were eventually pursued from Hurlburt Field. JB-2 testing at the Eglin Air Corps Proving Ground site on Santa Rosa Island did not begin until March 1947 over a year after launches at Range 64 ended. The delay between the activation of the 1st Experimental Guided Missiles Group at Eglin and

10961-481: Was assembled at Republic Aviation . The United States JB-2 was different from the German V-1 only slightly in dimensions. The wing span was only 2 + 1 ⁄ 2 inches (6.4 cm) wider and the length was extended less than 2 feet (61 cm). The difference gave the JB-2 60.7 square feet (5.64 m ) of wing area versus 55 square feet (5.1 m ) for the V-1. One of the few visible differences between

11074-408: Was becoming limited. The JB-2 was envisioned as a weapon to attack Japan. A 180-day massive bombardment of the Japanese Home Islands was being planned prior to the amphibious landing "by the most powerful and sustained pre-invasion bombardment of the war". Included in the assault were the usual naval bombardment and air strikes augmented by rocket-firing aircraft and JB-2s. Deployment of the JB-2 from

11187-411: Was considered against Japan's population and food crops. While large quantities of gas munitions were manufactured and plans were drawn, it is unlikely they would have been used. Richard B. Frank states that when the proposal reached Truman in June 1945, he vetoed the use of chemical weapons against personnel; their use against crops, however, remained under consideration. According to Edward J. Drea ,

11300-538: Was intended to capture the southern third of the southernmost main Japanese island, Kyūshū , with the recently captured island of Okinawa to be used as a staging area. In early 1946 would come Operation Coronet, the planned invasion of the Kantō Plain , near Tokyo , on the main Japanese island of Honshu . Airbases on Kyūshū captured in Operation Olympic would allow land-based air support for Operation Coronet. If Downfall had taken place, it would have been

11413-520: Was launched by a rocket-propelled sled along a 150 m (500 ft) long track, but seconds after release the JB-1 pitched up into a stall and crashed. This was caused by an incorrectly calculated elevon setting for take-off, but the JB-1 program was subsequently stopped, mainly because the performance and reliability of the GE B1 turbojet engines were far below expectations. In addition, the cost to produce

11526-403: Was modified to provide mid-course guidance for Loon. The Carbonero also carried a missile launcher. The LTV-N-2 was equipped with an AN/ANP-33 radar transponder. Shore based launches were tracked and controlled from aeither a SP-1W, SCR-584 or SV-4 radar. Submarine and ship radars were SV-1 type. Telemetry was supplied by either a AN/AKT-1A or AN/AKT-10. LTV-N-2 flights were terminated either by

11639-408: Was necessary. They supported mounting a large-scale thrust directly against the Japanese homeland, with none of the side operations that the Navy had suggested. Ultimately, the Army's viewpoint prevailed. Physically, Japan made an imposing target, distant from other landmasses and with very few beaches geographically suitable for sea-borne invasion. Only Kyūshū (the southernmost island of Japan) and

11752-502: Was not realistic that the entire Japanese population would be killed off, both American and Japanese officers at the time predicted a Japanese death toll in the millions. From the Battle of Saipan onward, Japanese propaganda intensified the glory of patriotic death and depicted the Americans as merciless "white devils." During the Battle of Okinawa, Japanese officers had ordered civilians unable to fight to commit suicide rather than fall into American hands, and all available evidence suggests

11865-599: Was recalled to Japan in February 1945 and given command of the Fifth Air Fleet on Kyūshū. The Fifth Air Fleet was assigned the task of kamikaze attacks against ships involved in the invasion of Okinawa, Operation Ten-Go , and began training pilots and assembling aircraft for the defense of Kyūshū, the first invasion target. The Japanese defense relied heavily on kamikaze planes. In addition to fighters and bombers, they reassigned almost all of their trainers for

11978-496: Was so serious that it threatened to derail planning. Ultimately, the Navy partially conceded, and MacArthur was to be given total command of all forces if circumstances made it necessary. The primary considerations that the planners had to deal with were time and casualties—how they could force Japan's surrender as quickly as possible with as few Allied casualties as possible. Before the First Quebec Conference ,

12091-718: Was the Allied C-in-C Pacific Ocean Areas , while Douglas MacArthur was Supreme Allied Commander, South West Pacific Area , and Admiral Louis Mountbatten was the Supreme Allied Commander, South East Asia Command . A unified command was deemed necessary for an invasion of Japan. Interservice rivalry over who it should be (the United States Navy wanted Nimitz, but the United States Army wanted MacArthur)

12204-482: Was the first step toward a system which would eventually be adapted for the forthcoming Martin MGM-1 Matador , the first operational surface-to-surface cruise missile built by the United States. The program at Holloman was terminated on 10 January 1949 after successful development of a radio guidance and control system that could control and even skid-land a JB-2 under the control of an airborne or ground transmitter. The 1st Experimental Guided Missile Group used JB-2s in

12317-557: Was the opening round of a struggle between the Army and Air Force over the guided missile which would last until the late 1950s. The end of the European War in May 1945 meant a reduction of the number of JB-2s to be produced, but not the end of the program. Army commanders in Europe had dismissed it as a weapon against Nazi Germany, as the strategic bombing concept was implemented and by 1945 the number of strategic targets in Germany

12430-522: Was the proposed Allied plan for the invasion of the Japanese home islands near the end of World War II . The planned operation was canceled when Japan surrendered following the atomic bombings of Hiroshima and Nagasaki , the Soviet declaration of war , and the invasion of Manchuria . The operation had two parts: Operation Olympic and Operation Coronet. Set to begin in November 1945, Operation Olympic

12543-633: Was to be a massive redeployment of units from the US Army's Southwest Pacific , China-Burma-India and European commands, among others. These would have included spearheads of the war in Europe such as the US First Army (15 divisions) and the Eighth Air Force. These redeployments would have been complicated by the simultaneous demobilization and replacement of highly experienced, time-served personnel, which would have drastically reduced

12656-541: Was to be mounted with resources already present in the Pacific, including the British Pacific Fleet , a Commonwealth formation that included at least eighteen aircraft carriers (providing 25% of the Allied air power) and four battleships. Tiger Force, a joint Commonwealth long-range heavy bomber unit, was to be transferred from RAF , RAAF , RCAF and RNZAF units and personnel serving with RAF Bomber Command in Europe. In 1944, early planning proposed

12769-411: Was used to start the engine. Acetylene was used for starting, and very often a panel of wood or similar was held across the end of the tailpipe to prevent the fuel from diffusing and escaping before ignition was complete. Once the engine had been started and the temperature rose to the minimum operating level, the external air hose and connectors were removed and the resonant design of the tailpipe kept

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