other sources the A-31 saw extensive front-line combat with the 10th Air Force located in China throughout the spring of 1944. As many as 60 A-31's could be fielded for a single mission. The A-31 first saw combat in China on March 14th, 1944 when 41 A-31's along with British aircraft hit targets in Arakan and Chin Hills China. It was last used on May 25, 1944 when 20 A-31's scored bombing hits on the Manipar R bridge at Tonzang. From April 1944, a number of Vengeance Mk IV series Is were made available to the 8th Air Force and assigned to target-towing flights and Combat Crew Replacement Center stations. All armament was removed and a light cable winch fitted in the rear fuselage for sleeve towing. Some of these aircraft continued to be flown with British national markings and serial numbers. By late June 1944, there were seven A-35Bs at RAF Cluntoe, seven at Greencastle, ten at RAF Sutton Bridge and six at RAF East Wretham. When the CCRCs were dissolved in the autumn, the Vengeances were transferred to combat groups, with most fighter and several bomber groups having one on hand at some time during 1945. A-35Bs did not show a high state of serviceability by this time and were generally considered troublesome to maintain. They were also designated RA-35B (R for Restricted) by this time. Variants RAF Variants Vengeance I Vultee V-72 license built by Northrop and ordered directly for Britain, powered by R-2600-A5B engine. 200 built. Vengeance IA Northrop built aircraft purchased under Lend-Lease, powered by R-2600-19 engine, otherwise similar to Vengeance I. USAAF designation A-31-NO. 200 built. Vengeance II Vultee built aircraft directly purchased by Britain. Small differences from Vengeance I. 501 built. Vengeance III Vultee built Lend-Lease aircraft. Similar to IA. USAAF designation A-31-VN. 200 built. Vengeance IV A-35B supplied under Lend-Lease to RAF and RAAF. 458 supplied to RAF and 121 to RAAF. USAAF Variants XA-31A Redesignated prototype Vengeance accepted by USAAF in June 1942. Vultee designation V-88. XA-31B XA-31A modified as testbed for 3,000 hp (2,240 kW) Pratt & Whitney XR-4360-1 Wasp Major. XA-31C Vengeance III modified as testbed for 2,200 hp (1,640 kW) Wright R-3350-18 Duplex Cyclone engine. One converted. YA-31C Vengeance IIIs modified as testbeds for R-3350-17 engines for B-29 Superfortress. Five built. A-35A Redesigned version for USAAF and Lend-Lease. 4° wing incidence. Powered by 1,700 hp (1269 kW) R-2600-13