He was chief of Fighter Command at the outbreak of World War II in 1939, a post he held through the Battle of Britain 10 July-12 Oct 1940. His refusal to commit more fighters to France in 1940, when he could see that the campaign was doomed, proved to be a vital factor in the later Battle of Britain, but his uncompromising attitude upset Churchill and other political leaders and he was replaced in Fighter Command Nov 1940. He retired 1942. KCB 1933, Baron 1943.