502d Bombardment Group The 502d Bombardment Group ( 502d BG ) was a World War II United States Army Air Forces combat organization . The unit was inactivated on 15 April 1946 . The unit served primarily in the Pacific Ocean theater of World War II as part of Twentieth Air Force . The 502d Bomb Group ' s aircraft engaged in very heavy bombardment B - 29 Superfortress operations against Japan . Its aircraft were identified by a " H " inside a diamond painted on the tail . History . The unit was established in early 1944 at Dalhart Army Air Field , Texas , being formed as a B - 29 Superfortress Very Heavy bombardment Group . The unit was formed with three reassigned bomb squadrons ( 402d , 411th and 430th ) . The 402d was formed in 1940 , becoming a II Bomber Command B - 24 Liberator Replacement Training Unit ( RTU ) ; the 411th and 430th having their origins as World War I Air Service Aero Squadrons . The 411th became a II Bomber Command B - 17 Flying Fortress RTU ; the 430th serving in the Panama Canal Zone as part of the Sixth Air Force before being inactivated . From an original group of 11 officers and 82 enlisted men , the 502d grew to three flying squadrons , a photo lab and thousands of personnel . In September 1944 , the newly formed group was sent to its training station at Grand Island Army Airfield , Nebraska . Due to a shortage of B - 29s , the group was equipped with former II Bomber Command B - 17 Flying Fortress es previously used for training heavy bomber replacement personnel . The 502d eventually received Atlanta - built B - 29B Superfortresses . The B - 29B was in fact unique , for it was equipped entirely with the only true variant of the B - 29 ever manufactured . These aircraft were actually stripped - down versions of the normal B - 29 , bereft of the General Electric gun system and a variety of other components , in order to save weight and increase bomb - carrying capacity . The resultant unladen weight of 69 , 000 pounds was a vast improvement , lessening the strain on engines and airframe and enabling the payload to be increased from 12 , 000 to 18 , 000 pound ordnance . The only armament on these aircraft was in the tail , where two . 50 caliber machine guns were installed . The elimination of the turrets and the associated General Electric computerized gun system increased the top speed of the Superfortress to 364 mph at 25 , 000 feet and made the B - 29B suitable for fast , unescorted hit - and - run bombing raids and photographic missions . In addition , the B - 29Bs of the 502nd were equipped with the new AN / APQ - 7 " Eagle " radar sets which gave a much clearer presentation of ground images through a wing - shaped radar vane slung beneath the fuselage . It also gave a biplane effect in appearance . The " Eagle " was the product of the Massachusetts Institute of Technology ' s Eagle radar development group . It had been designed especially for night missions . During World War II this special antenna and equipment for precision night radar missions was so secret that no B - 29s were ever shown with it , and there are no actual official photographs in existence . Missions had to be planned and prepared so that briefing material could be slanted from the radar point of view . The 502d was deployed to Pacific Theater of Operations ( PTO ) in late 1944 , being assigned to the XXI Bomber Command 315th Bombardment Wing in the Northern Mariana Islands ; being stationed at Northwest Field , Guam . Upon arrival the group ' s personnel were engaged in Quonset hut construction . By mid - July most personnel were able to move into the huts from the initial tents which they were assigned on arrival . On 9 July , the group flew a shakedown mission to Truk , carrying about half a normal payload of bombs . The group entered combat on 30 June 1945 when the group bombed enemy installations on Rota . It then began flying very long range strategic bombardment missions over the Japanese Home Islands , principally attacking targets relating to the enemy ' s petroleum industry . The 502d was awarded a Distinguished Unit Citation ( DUC ) for attacks on the coal liquefaction plant at Ube , the tank farm at Amagasaki and the Nippon oil refinery at Tsuchizaki in August 1945 . It also conducted night incendiary raids attacking major Japanese cities causing massive destruction of urbanized areas . The group continued strategic bombing raids and incendiary attacks until the Japanese Capitulation in August 1945 . After V - J Day , the 502d dropped supplies to Allied prisoners , participated in show - of - force missions , and flew over Japan to evaluate bombardment damage . In the fall of 1945 , the group largely demobilized as part of the " Sunset Project " , with some aircraft being sent reclamation on Tinian ; others being returned to the United States for storage at aircraft depots in the southwest . By Christmas , the group fleet was reduced to 30 or less planes and the remaining elements of the group was effectively consolidated into the 501st Bombardment Group . Many of the remaining veterans signed for " any conditions of travel " to get home , arriving three weeks later in Oakland , California , where troop trains scattered them for points of discharge close to their homes . The 502d was inactivated on Guam largely as a paper unit on 15 April 1946 .