(Schlacht)/LG 2 (2nd ground attack group of the 2nd demonstration wing) he flew as a Leutnant (Second Lieutenant) and pilot during the Invasion of Poland and Battle of France.

The group was responsible of repelling a large enemy tank formation north of Cambrai on 17 May 1940 which threatened the flank of the German advance.

[3] Dörffel was shot down twice during the campaign in the west, the first time on 14 May 1940 near Tirlemont, Belgium and in June 1940 near Dunkirk.

[2] With the beginning of Operation Barbarossa, the German invasion of the Soviet Union in June 1941, Dörffel was transferred to the Eastern Front, particularly in support of the central and southern sectors, providing air support to the German ground forces.

In early October 1943 he flew 19 combat missions on one day against the attacking Red Army forces crossing the Dnieper River near Kiev.

He flew his 1,000th combat mission of the war on 6 October 1943, claiming his 30th aerial victory on that flight.

Dörffel was forced to bail out of his Focke-Wulf Fw 190 F-8 (Werknummer—factory number—580 464) following an attack on a four-engined bomber formation.