The squadron was first activated as the 21st Photographic Reconnaissance Squadron in September 1942 at Peterson Field, Colorado, USA, but apparently was not fully manned until December. It trained there until April 1943, when the squadron was reassigned from 5th Photographic Group and began its overseas movement.  The squadron arrived in India in June and began deploying flights to China the following month. It served as an umbrella organization for Fourteenth Air Force reconnaissance operations in China. The squadron deployed detached flights of reconnaissance aircraft (mostly specially equipped Lockheed F-5 Lightnings and North American F-4 and F-6 Mustangs), which flew combat reconnaissance missions over Japanese-held territory from numerous forward airstrips. Squadron detachments flew missions over India, Burma, Thailand, French Indochina, Hainan Island, Formosa, Shanghai, China, the Philippines, Japan and Korea.  Flight A of the squadron also performed mapping missions over Thailand and Burma. The squadron redeployed from China at the end of 1945 and was inactivated at Fort Lawton, Washington, at the beginning of 1946. Source: Revolvy.