Winston Churchill first became Prime Minister of the United Kingdom in 1940. He took office on 10 May 1940, succeeding Neville Chamberlain during the opening phase of the Second World War.
Churchill's appointment came as Germany launched its invasion of western Europe. Chamberlain's government had lost political support after the Norway Debate, and King George VI asked Churchill to form a government. Churchill then led a coalition administration that included members of both the Conservative and Labour parties.
The year 1940 is sometimes confused with 1941 or 1942 because many of Churchill's best-known wartime speeches and decisions came later. His first premiership lasted until 26 July 1945, when Labour's Clement Attlee became Prime Minister after the general election. Churchill returned to office for a second, separate premiership in 1951, serving until 1955.