Luftflotte 4 carried out the bombing of Warsaw, Poland in September 1939 and of Belgrade, Yugoslavia in April 1941. Löhr had developed a plan to bomb Belgrade with incendiary bombs first, so that the fires would help the second, nighttime, attack to find the targets. This cost thousands of people their lives. Löhr was promoted to colonel general effective 3 May 1941. He commanded the 12th Army from 12 July 1942 through to December 1942.