It was led by Winston Churchill, who was appointed prime minister of the United Kingdom by King George VI following the resignation of Neville Chamberlain in the aftermath of the Norway Debate.

At the outset, Churchill formed a five-man war cabinet which included Chamberlain as Lord President of the Council, Clement Attlee as Lord Privy Seal and later as Deputy Prime Minister, Viscount Halifax as Foreign Secretary, and Arthur Greenwood as a minister without portfolio.

Although the original war cabinet was limited to five members, in practice they were augmented by the service chiefs and ministers who attended the majority of meetings.

The cabinet changed in size and membership as the war progressed but there were significant additions later in 1940 when it was increased to eight after Churchill, Attlee, and Greenwood were joined by Ernest Bevin as Minister of Labour and National Service; Anthony Eden as Foreign Secretary, replacing Halifax who was sent to Washington as Ambassador to the United States; Lord Beaverbrook as Minister of Aircraft Production; Sir Kingsley Wood as Chancellor of the Exchequer; and Sir John Anderson as Lord President of the Council, replacing Chamberlain who died in November (Anderson later became chancellor following Wood's death in September 1943).

The coalition was dissolved in May 1945, following the final defeat of Germany, when the Labour Party decided to withdraw in order to prepare for a general election.

It was known as the Churchill caretaker ministry and managed the country's affairs until the completion of the general election on 26 July that year.

In talks at Downing Street with Viscount Halifax and Churchill, he indicated that he was quite ready to resign if that was necessary for Labour to enter such a government.

[4] Churchill's version gets the date wrong, and he fails to mention the presence of David Margesson, the government Chief Whip.

[4][5][6] Halifax's account omits the dramatic pause and gives an additional reason: "PM said I was the man mentioned as most acceptable.

[8] Labour's Hugh Dalton, however, noted in his diary entry for 9 May that he had spoken with Attlee, who "agrees with my preference for Halifax over Churchill, but we both think either would be tolerable".

Chamberlain initially felt that a change of government at such a time would be inappropriate, but upon being given confirmation that Labour would not serve under him, he announced to the war cabinet his intention to resign.

Their conference went on into the early hours of Saturday and they reached a broad agreement on the composition of the new war cabinet, subject to Labour Party confirmation.

Attlee and Greenwood were confident of securing this on Saturday after Churchill promised that more than a third of government positions would be offered to Labour members, including some of the key posts.

[13][14] On Saturday, 11 May, the Labour Party agreed to join a national government under Churchill's leadership and he was able to confirm his war cabinet.

The Labour Party appointed an acting Leader of the Opposition whose job, although he was in effect a member of the national government, was to ensure the continued functionality of the House of Commons.

[18] The main problem for Churchill as he became prime minister was that he was not the leader of the majority Conservative Party and, needing its support, was obliged to include Chamberlain in the war cabinet, but this was not to Labour's liking.

From 1942, as the tide of war began to turn in favour of the Allies, the importance of the CDC was reduced and its meetings became fewer as its work was increasingly delegated or raised at conferences.

The CDC enabled Churchill to have direct contact with them so that strategic concerns could be addressed with due regard to civil matters and foreign affairs.

[25] Ismay's role, technically, was Secretary of the CSC but he was in fact Churchill's chief staff officer and military adviser throughout the war.

A specially convened sitting of the House of Commons was held and Churchill spoke for the first time as Prime Minister:[26] I beg to move, that this House welcomes the formation of a Government representing the united and inflexible resolve of the nation to prosecute the war with Germany to a victorious conclusion.He explained that a war cabinet of five members had been formed to represent the unity of the nation with all three main party leaders agreeing to serve either in the war cabinet or in high executive office.

Even so, his speech has become one of his most famous because he concluded with his statement of intent:[27] I would say to the House, as I said to those who have joined this Government: "I have nothing to offer but blood, toil, tears and sweat".

At this time I feel entitled to claim the aid of all, and I say, "Come then, let us go forward together with our united strength".In reply, Hastings Lees-Smith as acting Leader of the Opposition announced that Labour would vote for the motion to assure the country of a unified political front.

[30] Apart from a handful of junior appointments such as royal household positions, Churchill completed the construction of his government by the end of his first week in office.

[31] The war situation in Europe became increasingly critical for the Allies as the Wehrmacht overran northern France and the Low Countries through May, culminating in the siege of Dunkirk and the desperate need to evacuate the British Expeditionary Force by Operation Dynamo.

Halifax wanted to sue for peace by asking Benito Mussolini to broker a treaty between the British government and Hitler.

Churchill agreed and his new ministry, essentially a Conservative one, held office for the next two months until it was replaced by Attlee's Labour government after their election victory.

This table lists the junior offices (often ministerial level 3) whose titles signify an assistant, deputy or under-secretary function.