The first Bf-109G “Gustav” entered service in March 1942. New features were a pressurized cockpit with three larger guns mounted on the nose and none on the wings but could be field mounted. The Bf-109G could overheat causing oil leaks; starting a fire forcing the pilot to bail out. The Gustav was produced in many variants including long-range fighters, recon fighters and bomber destroyers. The Bf-109G-6 lacked a pressurized cockpit but was the most numerous Bf-109 produced and the first to carry 13mm machine guns; equivalent to the American 50 caliber Browning.

In the summer of 1941 Heinrich Bartels joined JG 26 on the Western Front. On August 19 he scored his first victory. On January 27, 1942 Bartels transferred to 11./JG 1 which soon became 8./JGF 5 and where he scored 47 victories. In the spring of 1943 Bartels transferred to 11./JG 27 in the Mediterranean theater. On November 17, 1943 while in Greece he displayed his 70th victory bar on the rudder of Red 13 WNr. 27 169. Bartels final victory total was 99 when on December 23, 1944 he didn’t return.