from the older Soviet-made combat aircraft to newer American-made aircraft, however, the CAF continued combat operations with Soviet-made aircraft in this interim period, including a major offensive-strike operation on 22 January 1942, in which CAF Tupolev SB-2 bombers from Taipingsi air base in Sichuan, rendezvoused with AVG fighter escorts (a total of over four dozen aircraft), and flying to Gia Lam Airport in Vietnam to bomb the occupying Japanese forces based there; Major Shao Ruilin who commanded from an SB-2 was shot down by anti-aircraft fire and was killed over Hanoi. By the time the American Volunteer Group was officially disbanded on 4 July 1942, the United States had been a combatant in World War II for nearly seven months. Chennault was recalled to active duty in the United States Army Air Forces (USAAF); he was promoted to brigadier general to take command of the China Air Task Force (CATF), which was established on 14 July 1942 as a part of the 10th Air Force of USAAF. The 10th Air Force was activated on 12 February 1942 for operations in the China-Burma-India theatre of the war. Later in June 1942, Chennault was given the command of the 10th Air Force after the transfer of Commanding General Lewis Brereton to Egypt on 6 June 1942. The CATF included the four squadrons of P-40s of the 23rd Fighter Group and the 11th Bomber Group of B-25 Mitchells. Many of the fighter pilots in the CATF were former pilots of the Flying Tigers. One of the aircraft contracts to be funded by the American Lend-Lease was to supply China with 125 P-43 Lancer fighter planes. In early 1942, shipments began of the P-43s in crates to China via Karachi, India, and they included some Vultee P-66 Vanguard fighters. The 4th Air Group of the Chinese Air Force was selected to receive and ferry the P-43s from India to Kunming. Many were lost in test flights and ferrying accidents. By August 1941, according to Chinese sources, the Chinese Air Forces received 41 operable P-43s. The 4th Air Group was sent to Chengdu to train on the new P-43s, and joined in the defense of Chengdu with the I-15s of the 17th Squadron and I-16s of the 29th Squadron. During the first half of 1942, there were few combat operations by pilots of the Chinese Air Force. As of 13 August 1942, Chennault's CATF had