[243] The exchange program “appears to have originated with the participation--at Tactical Air Command’s invitation--of two Marine Corps and two Navy pilots ... in the fall of 1947.” Within two years, the program designed to “indoctrinate selected Air Force and Navy pilots in the air operational and air training activities of each other’s service, had received Department of Defense approval.” On 1 October 1949 the program went into effect. Initially the exchange period was one year, but after the Korean fighting broke out, the period was reduced to approximately three months. Marine participation began late in 1951. Atch 1 to Hq, USAF (AFCHO) memo to Maj J. M. Yingling, HQMC, dtd 16 Jan 67 in v. V, Korean comment file. [244] On 15 September, Major Gillis had shot down a solo MIG-15. Another feat, this one a study in determination and perseverance, had occurred early in the summer. On 22 July, the VMJ-1 commander, Lieutenant Colonel Vernon O. Ullman, had taken to the air for a photo mission over North Korea in the vicinity of Sinanju, located near the Yellow Sea 40 miles above Pyongyang. During the first of seven scheduled flights, he encountered heavy flak but nevertheless completed his first mapping run in the area. Further, the Marine flier decided that the antiaircraft menace was not going to force him to abandon the remaining part of his task. He continued. On the second of his seven runs, some 40 enemy jets (MIG-15s) appeared on the scene. These were dissuaded from close-in interference, however, by the photo escort of 24 USAF single-engine Sabrejet fighters. Thereafter, the Russian-made aircraft disappeared; Lieutenant Colonel Ullman continued, despite the intense, accurate enemy antiaircraft fire, until he concluded his mission.