To invade England Germany needed mastery of the air and the English Channel. The Luftwaffe began attacking convoys and shipping in the Channel on July 10th and by August 1940 the Luftwaffe set out to overpower the RAF with strikes against airfields in southern England. On August 25th a single German plane accidentally attacked London and the British mounted a retaliatory strike against Berlin that night. This caused the change in tactics to start attacking cities rather than RAF installations. This was the turning point in the Battle of Britain which ended on Sept 15th with the invasion postponed. In June 1941 Germany invaded Russia and the Luftwaffe destroyed over 4,000 Russian aircraft in a month. By April 1944 the tide had turned against the Axis and defending the Reich became the major effort of the Luftwaffe that included the introduction of the first combat jet, the ME 262. Germany’s air force lost over 100,000 aircraft between 1939 and 1945.