A decorated World War I aviator, he returned to military service in 1934 as an Oberstleutnant in the Luftwaffe.

During the invasion of Poland, Förster, by now a Generalmajor, commanded the Luftwaffen-Lehrdivision with significant success.

He was then appointed as chief of staff of the 5th Air Fleet during the invasion of Norway.

After serving on the German-French Peace Commission, he was appointed as military governor of the German-occupied territory of Serbia from April to June 1941, then commanded the 1st Air Corps during the invasion of the Soviet Union until October 1942.

He spent the remainder of the war as chief of administration at the Reich Ministry of Aviation.