By the beginning of World War II, Felmy commanded Air Fleet 2 (Luftflotte 2) of the Luftwaffe.

While Felmy was a General der Flieger, he was not responsible for commanding the air force component of the Special Staff.

From 1942 to 1943, he remained in Greece and commanded a "special deployment" (zur besonderen Verwendung, or z. b. V.) unit named after him (z. b. V. Felmy).

[5] In 1945, the XXXIV Corps was defeated during the Yugoslav Partisan General Offensive of March and April.

In 1948, during the Hostages Trial in Nuremberg, Felmy was convicted of war crimes in Greece and was given a sentence of 15 years.