Winston Churchill was appointed First Lord of the Admiralty on 3 September 1939, the day that the United Kingdom declared war on Nazi Germany. He succeeded Neville Chamberlain as prime minister on 10 May 1940 and held the post until 26 July 1945. Out of office during the 1930s, Churchill had taken the lead in calling for British re-armament to counter the growing threat of militarism in Nazi Germany. As prime minister, he oversaw British involvement in the Allied war effort against the Axis powers. Churchill is seen as a victorious wartime leader who played an important role in defending Europe's liberal democracy against the spread of fascism, though some wartime events like the 1945 bombing of Dresden have generated controversy. He was the most important of the Allied leaders during the first half of the Second World War.