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. Regarded as the most important of the Allied leaders during the first half of the Second World War, Historians have long held Churchill in high regard as a wartime leader who played an important role in defending Europe's liberal democracy against the spread of fascism. For his wartime leadership and for his contributions in overseeing the war effort, he has been consistently ranked both by scholars and the public as one of the top three greatest British prime ministers, often seen as the greatest prime minister in British history.

First Lord of the Admiralty: September 1939 to May 1940 The Phoney War and the Norwegian Campaign

On 3 September 1939, the day Britain declared war on Germany following the outbreak of the Second World War, Chamberlain appointed Churchill as First Lord of the Admiralty, the same position he had held at the beginning of the First World War. As such he was a member of Chamberlain's war cabinet. Churchill later claimed that, on learning of his appointment, the Board of Admiralty sent a signal to the Fleet: "Winston is back". Although this story was repeated by Lord Mountbatten in a speech at Edmonton in 1966, Richard M. Langworth notes that neither he nor Churchill's official biographer Martin Gilbert have found contemporary evidence to confirm it, suggesting that it may well be a later invention.

As First Lord, Churchill proved to be one of the highest-profile ministers during the so-called "Phoney War", when the only significant action by British forces was at sea. Churchill was ebullient after the Battle of the River Plate on 13 December 1939 and afterwards welcomed home the crews, congratulating them on "a brilliant sea fight" and saying that their actions in a cold, dark winter had "warmed the cockles of the British heart". On 16 February 1940, Churchill personally ordered Captain Philip Vian of the destroyer HMS Cossack to board the German supply ship Altmark in Norwegian waters and liberate some 300 British prisoners who had been captured by the Admiral Graf Spee. These actions, supplemented by his speeches, considerably enhanced Churchill's reputation.

He was concerned about German naval activity in the Baltic Sea and initially wanted to send a naval force there but this was soon changed to a plan, codenamed Operation Wilfred, to mine Norwegian waters and stop iron ore shipments from Narvik to Germany. There were disagreements about mining, both in the war cabinet and with the French government. As a result, Wilfred was delayed until 8 April 1940, the day before the German invasion of Norway was launched.

The Norway Debate and Chamberlain's resignation

After the Allies failed to prevent the German occupation of Norway, the Commons held an open debate from 7 to 9 May on the government's conduct of the war. This has come to be known as the Norway Debate and is renowned as one of the most significant events in parliamentary history. On the second day (Wednesday, 8 May), the Labour opposition called for a division which was in effect a vote of no confidence in Chamberlain's government. There was considerable support for Churchill on both sides of the House but, as a member of the government, he was obliged to speak on its behalf. He was called upon to wind up the debate, which placed him in the difficult position of having to defend the government without damaging his own prestige. Although the government won the vote, its majority was drastically reduced amid calls for a national government to be formed.

In the early hours of 10 May, German forces invaded Belgium, Luxembourg and the Netherlands as a prelude to their assault on France. Since the division vote, Chamberlain had been trying to form a coalition but Labour declared on the Friday afternoon that they would not serve under his leadership, although they would accept another Conservative. The only two candidates were Churchill and Lord Halifax, the Foreign Secretary. The matter had already been discussed at a meeting on the 9th between Chamberlain, Halifax, Churchill, and David Margesson, the government Chief Whip. Halifax admitted that he could not govern effectively as a member of the House of Lords and so Chamberlain advised the King to send for Churchill, who became prime minister. His first act was to write to Chamberlain and thank him for his support.

Churchill later wrote of feeling a profound sense of relief in that he now had authority over the whole scene. He believed himself to be walking with destiny and that his life so far had been "a preparation for this hour and for this trial".

Prime Minister: 1940–1945

Dunkirk to Pearl Harbor: May 1940 to December 1941

Initial reaction to Churchill as Premier In May, Churchill was still unpopular with many Conservatives, with probably the majority of the Labour Party, and with the so-called Establishment – Jenkins says his accession to the premiership was "at best the equivalent of an abrupt wartime marriage". He probably could not have won a majority in any of the political parties in the House of Commons, and the House of Lords was completely silent when it learned of his appointment. Chamberlain remained Conservative Party leader until October when ill health forced his resignation – he died of cancer in November. By that time, Churchill had won the doubters over and his succession as party leader was a formality. Ralph Ingersoll reported in November: "Everywhere I went in London people admired [Churchill's] energy, his courage, his singleness of purpose. People said they didn't know what Britain would do without him. He was obviously respected. But no one felt he would be prime minister after the war. He was simply the right man in the right job at the right time. The time being the time of a desperate war with Britain's enemies".

War ministry created

The war energised Churchill, who was 65 years old when he became prime minister. Stating that he was the only top leader from World War I who still had an important political job, John Gunther wrote in 1940 that Churchill "looks ten years younger than he is". Hubert Renfro Knickerbocker wrote in 1941 that "The responsibilities which are his now must be greater than those carried by any other human being on earth. One would think such a weight would have a crushing effect upon him. Not at all. The last time I saw him, while the Battle of Britain was still raging, he looked twenty years younger than before the war began  ... His uplifted spirit is transmitted to the people".

Churchill began his premiership by forming a five-man war cabinet which included Chamberlain as Lord President of the Council, Labour leader Clement Attlee as Lord Privy Seal (later as deputy prime minister), Halifax as Foreign Secretary and Labour's Arthur Greenwood as a minister without portfolio. In practice, these five 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. By the end of 1940, it had 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, D.C. 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 after Kingsley Wood's death in September 1943). Jenkins described this combination as a "war cabinet for winning", contrasting it with Chamberlain's "war cabinet for losing". In response to previous criticisms that there had been no clear single minister in charge of the prosecution of the war, Churchill created and took the additional position of Minister of Defence, making him the most powerful wartime prime minister in British history.

Churchill wanted people he knew and trusted to take part in government. Among these were personal friends like Beaverbrook and Frederick Lindemann, who became the government's scientific advisor. Lindemann was one of several outside exports drafted in and these "technocrats" fulfilled vital functions, especially on the Home Front. Churchill would proudly proclaim that his government, in the interests of national unity, was the most broadly based in British political history as it spanned far right to far left by including such figures as Lord Lloyd on the right and Ellen Wilkinson on the left.

Resolve to fight on

At the end of May, with the British Expeditionary Force in retreat to Dunkirk and the Fall of France seemingly imminent, Halifax proposed that the government should explore the possibility of a negotiated peace settlement using Mussolini as an intermediary given that Italy was still neutral. There were several high-level meetings from 26 to 28 May, including two with the French premier Paul Reynaud. Churchill's resolve was to fight on, even if France capitulated, but his position remained precarious until Chamberlain resolved to support him. Churchill had the full support of the two Labour members but knew he could not survive as prime minister if both Chamberlain and Halifax were against him. In the end, by gaining the support of his outer cabinet, Churchill outmanoeuvred Halifax and won Chamberlain over. The essence of Churchill's argument was that, as he said, "it was idle to think that, if we tried to make peace now, we should get better terms than if we fought it out". He therefore concluded that the only option was to fight on though, at times, he personally was pessimistic about the chances of a British victory, as on 12 June 1940 when he told General Hastings Ismay that "[y]ou and I will be dead in three months' time". Nonetheless, his use of rhetoric hardened public opinion against a peaceful resolution and prepared the British people for a long war – Jenkins says Churchill's speeches were "an inspiration for the nation, and a catharsis for Churchill himself".

Importance of Churchill's wartime speeches

Churchill's wartime speeches were a great inspiration to the embattled British, beginning with his first as prime minister, which he had delivered to the Commons on 13 May: the "blood, toil, tears and sweat" speech. It was not well-received at the time, mainly because the majority of Conservative MPs held doubts about Churchill's suitability to be premier. It was in fact little more than a short statement but, Jenkins says, "it included phrases which have reverberated down the decades". Churchill made it plain to the nation that a long, hard road lay ahead and that victory was the final goal:

Dunkirk evacuation and the Battle of France Operation Dynamo, the evacuation of 338,226 Allied servicemen from Dunkirk, ended on Tuesday, 4 June when the French rearguard surrendered. The total was far in excess of expectations and it gave rise to a popular view that Dunkirk had been a miracle, and even a victory. Churchill himself referred to "a miracle of deliverance" in his "we shall fight on the beaches" speech to the Commons that afternoon, though he shortly reminded everyone that: "We must be very careful not to assign to this deliverance the attributes of a victory. Wars are not won by evacuations". The speech ended on a note of defiance coupled with a clear appeal to the United States: