Actually the 109F-4 is a 1941 aircraft. The first F-4s reached frontline units in June 1941. The first of the F-series is from 1940. Mölders and JG 51 flew the 109F-1 over England from early October 1940, so technically it even took part in the Battle of Britain. In its time it was the best fighter in the world by a significant margin.