German World War II Fighter Ace. At the age of 20, Mayer joined the Luftwaffe and spent two years in training until he was transferred to the Jagdgeschwader 2 in December of 1939. Seven months later, Mayer claimed his first aerial victory shooting down a French Morane fighter on June 13. Throughout the year, Mayer rose through the ranks and claimed more air victories, having reached twenty confirmed victories and the rank of Oberleutnant by August 1941. In that same month, he also received the Knight's Cross of the Iron Cross for extreme bravery. By the end of next year, Mayer had been promoted again to Hauptmann and appointed as the Gruppenkommandeur of III./JG 2. He had also claimed his first victories against the United States Army Air Forces, shooting down three bombers on November 23, 1942. These three victories brought his total up to 55 confirmed. On April 6, 1943, Mayer claimed his 63rd and 64th air victories and was awarded with the Oak Leaves to the Knight's Cross. As an Oberstleutnant, he was appointed as Geschwaderkommodore of JG 2 after Oberst Walter Oesau was assigned to a different command, on July 1, 1943. On February 6, 1944, Mayer claimed his last two victories, bringing his total up to 102, becoming the first fighter pilot to claim over 100 victories entirely on the Western Front. In addition, he was the leading Viermot-Experte, or heavy bomber killer, of the Luftwaffe, with 26 victories. On his 353rd mission on March 2, 1944, he was shot down 1.5 miles south of Montmédy, France, by P-47 Thunderbolts after taking hits to the nose and cockpit area. Mayer was posthumously awarded the Swords to the Knight's Cross on the same day he was killed.