Mors was born on 20 June 1921 in Sigmaringen, at the time in the Province of Hohenzollern within the Weimar Republic.

The Staffel was based at an airfield at Petsamo, present-day Pechenga in Murmansk Oblast, Soviet Union on the Eismeerfront (Ice Sea Front)—the area of operations nearest the Arctic Ocean.

On this mission, Mors was the wingman of Theodor Weissenberger and shot down a Hawker Hurricane fighter.

Mors was one of the pilots who shuttled one of the aircraft from Krasnogvardeysk, present-day Gatchina, to Alakurtti Air Field.

[6] For these claims, Mors received the Iron Cross 1st Class (Eisernes Kreuz erster Klasse).

[8] Following aerial combat 15–20 kilometers (9.3–12.4 miles) northwest of Murmashi on 15 June 1943, Mors was forced to bail out of his Bf 109 G-2 (Werknummer 13 764—factory number), sustaining minor injuries.

Three days later, Mors was spotted and rescued by an Arado Ar 196 aircraft and returned to his unit.

Gruppe was ordered to relocate further south to the front near Nevel, Leningrad and Lake Ilmen.

[13] Here on 20 March, Mors became an "ace-in-a-day" when he claimed eight aerial victories, six Ilyushin Il-2 ground-attack aircraft and two P-40 fighters.

[14] On 13 April, Mors claimed three Yakovlev Yak-9 fighters shot down on a Junkers Ju 87 dive bomber escort mission.

To counter the invasion, elements of I. Gruppe of JG 5 were transported to France by train that afternoon.

The ground personnel were flown on Junkers Ju 52s to their airfield at Montdidier, 35 km (22 mi) south of Amiens.

[20] Here on 7 July, I. Gruppe took off at 18:15 and engaged a formation of approximately 20 United States Army Air Forces (USAAF) Republic P-47 Thunderbolt fighters.

Lehner managed to make crash landing, sustaining burn injuries to his face, a broken nose and a concussion.

[28] Spick also lists him with 60 aerial victories, 48 of which on the Eastern Front and 12 over the Western Allies, including one four-engine heavy bomber, claimed in an unknown number of combat missions.