Hartmann joined the Luftwaffe in 1941 and was deployed to fighter squadron JG-52 in October 1942, on the Eastern Front in the Soviet Union. Assigned to fly Bf-109 fighters, Hartmann shot down his first Soviet plane and soon established himself as one of the most talented pilots of the war.
Germany's fortunes began to fall apart in 1943, beginning with a terrible defeat in the Battle of Stalingrad, but Hartmann shot down planes at a record pace. In July 1943, he was made captain of his squadron, and shot down seven planes in a single day during the Battle of Kursk. After reaching 250 victories he was grounded by Luftwaffe chief of staff Hermann Goring, who was fearful of the possibility the hero might die in combat. However, Hartmann successfully lobbied to be reinstated as a combat pilot.
At war's end Hartmann was imprisoned by the Soviet Union as a war criminal. He was released in 1955 and returned to West Germany, where he was reunited with his wife, to whom he had written every day of the war. Hartmann often said that he was more proud of the fact that he had never lost a wingman in combat than he was about his rate of kills.