At the time of his retirement in June 1939, Dowding was asked to stay on until March 1940 because of the tense international situation. He was again permitted to continue through the Battle of Britain, first until July and finally until November 1940. In 1940, Dowding, nicknamed "Stuffy" by his men for his alleged lack of humour, proved unwilling to sacrifice aircraft and pilots in the attempt to aid Allied troops during the Battle of France. He, along with his immediate superior Sir Cyril Newall, then Chief of the Air Staff, resisted repeated requests from Winston Churchill to weaken the home defence by sending precious squadrons to France. When the Allied resistance in France collapsed, he worked closely with Air Vice-Marshal Keith Park, the commander of 11 Fighter Group, in organising cover for the evacuation of the British Expeditionary Force at Dunkirk.