421st Air Refueling Squadron The 421st Air Refueling Squadron is an inactive United States Air Force unit . It was last assigned to the 41st Air Division at Yokota Air Base , Japan , where it was inactivated on 18 February 1965 . In 1985 the squadron was consolidated with the 421st Bombardment Squadron , Very Heavy , a World War II very heavy bombardment squadron that participated in the air offensive against Japan with Twentieth Air Force before moving to Clark Field , Philippines , where it was inactivated in 1946 . Since consolidation the squadron has not been active . History . World War II . The 421st Bombardment Squadron was activated on paper in March 1944 at Dalhart Army Air Field , Texas as a Boeing B - 29 Superfortress very heavy bombardment squadron . It moved to Fairmont Army Airfield , Nebraska the day after activation , where it received its initial cadre from the 9th Bombardment Group . Because of aircraft availability , initial training missions were flown with Boeing B - 17 Flying Fortress aircraft . Once the squadron competed training , it moved to North Field , Tinian in the Mariana Islands of the central Pacific area in January 1945 and beame part of the XXI Bomber Command of Twentieth Air Force . Its mission was the strategic bombardment of the Japanese Home Islands and the destruction of Japan ' s war - making capability . The 421st flew " shakedown " missions against Japanese targets on Moen Island , Truk , and other points in the Carolines and Marianas . The squadron began combat missions over Japan on 25 February 1945 with a firebombing mission over northeast Tokyo . The 421st continued to participate in wide area firebombing attack , but the first ten - day blitz resulted in the command running out of incendiary bombs . After that the squadron flew conventional bombing missions using high explosive bombs . The squadron earned two Distinguished Unit Citation s for its attack on the industrial center of Yokohama in May 1945 and mining shipping lanes in the Shimonoseki Strait between Korea and Japan in July and August . The squadron continued attacking urban areas of major Japanese cities with incendiary ordnance until the end of the war in August 1945 , causing massive destruction of urbanized areas . It also conducted raids against strategic objectives , bombing aircraft factories , chemical plants , oil refineries , and other targets in Japan . The squadron flew its last combat missions on 14 August when hostilities ended . Afterwards , its B - 29s carried relief supplies to Allied prisoner of war camps in Japan and Manchuria . The squadron was largely demobilized on Tinian during the fall of 1945 . It remained in the western Pacific . The 421st moved to Clark Field in the Philippines in March 1946 . It was inactivated at Clark on June 15 , 1946 . The squadron ' s low - hour aircraft were flown to storage depots in the United States . Cold War . The 421st Air Refueling Squadron ' s origins were in an advanced detachment of tankers assigned to the 98th Bombardment Wing , which moved to Yokota Air Base , Japan from Spokane AFB , Washington . Shortly after arrival at Yokota , the Detachment was replaced by the 421st Air Refueling Squadron , which assumed its mission , equipment , and personnel . The mission of the squadron was to provide dedicated air refueling for in - flight refueling capable Far East Air Force ( later Pacific Air Forces ) bombers , fighters , and fighter bombers . The squadron was initially equipped with transferred Strategic Air Command ( SAC ) KB - 29M Stratofortress bomber s that were converted to tankers using a British - developed hose refueling system . The squadron upgraded to KB - 50 Superfortress tankers in 1958 which provided greater speed to refuel jet aircraft . KB - 50s were modified about 1959 to KB - 50J configuration which added a J - 47 turbojet engine underneath each wing in place of the auxiliary fuel tanks to increase the speed of the aircraft . Some aircraft and crews deployed to Don Muang Royal Thai Air Force Base , Thailand in 1961 to support USAF advisory tactical jet aircraft . Some of these aircraft ran low on fuel while still over South Vietnam . Some of the refuelings were carried out at such low altitudes that they came under hostile ground fire . By 1964 the unit possessed almost all of the KB - 50s remaining in the Air Force inventory , but its aircraft began to show signs of corrosion and structural fatigue . They were taken out of service in 1965 , but it was considered too risky to fly them across the Pacific to storage at the Military Aircraft Storage and Disposal Center at Davis - Monthan AFB , Arizona . The squadron ' s aircraft were scrapped on their hardstands at Yokota . The squadron inactivated ans its mission was assumed by SAC Boeing KC - 97 Stratotanker s and Boeing KC - 135 Stratotanker s . Lineage . 421st Bombardment Squadron 421st Air Refueling Squadron