On 3 September 1939, the day Britain declared war on Germany following the outbreak of the Second World War, Churchill was appointed First Lord of the Admiralty, the same position he had held during the first part of the First World War. As such he was a member of Chamberlain's small War Cabinet.
In this position, he proved to be one of the highest-profile ministers during the so-called "Phoney War," when the only noticeable action was at sea and the USSR's attack on Finland. Churchill advocated the pre-emptive occupation of the neutral Norwegian iron-ore port of Narvik and the iron mines in Kiruna, Sweden, early in the war. However, Chamberlain and the rest of the War Cabinet disagreed, and the operation was delayed until the successful German invasion of Norway.
"We shall never surrender"
Churchill wears a helmet during an air raid warning in the Battle of Britain in 1940
On 10 May 1940, hours before the German invasion of France by a lightning advance through the Low Countries, it became clear that, following failure in Norway, the country had no confidence in Chamberlain's prosecution of the war and so Chamberlain resigned. The commonly accepted version of events states that Lord Halifax turned down the post of prime minister because he believed he could not govern effectively as a member of the House of Lords instead of the House of Commons. Although the prime minister does not traditionally advise the King on the former's successor, Chamberlain wanted someone who would command the support of all three major parties in the House of Commons. A meeting between Chamberlain, Halifax, Churchill and David Margesson, the government Chief Whip, led to the recommendation of Churchill, and, as constitutional monarch, George VI asked Churchill to be prime minister. Churchill's first act was to write to Chamberlain to thank him for his support.