Kittel joined the Luftwaffe in 1939, at the age of 22 and flew his first combat missions in 1941. In spring 1941, he joined "Jagdgeschwader 54" (JG 54) supporting Army Group North on the Eastern Front. Kittel claimed his first victory on 22 June 1941, the opening day of "Operation Barbarossa". Kittel took time to amass his personal tally of aerial victories. By February 1943, he reached 39 kills, relatively insignificant when compared with some other German aces. In 1943, his tally began to increase when JG 54 began to operate the Fw 190. Kittel earned the Knight's Cross of the Iron Cross ("Ritterkreuz des Eisernen Kreuzes") on 29 October 1943, for reaching 120 aerial victories. By the time he was awarded the decoration he had a tally of 123 victories. Many of the Soviet aircraft shot down by Kittel were IL-2 Shturmoviks.