Within weeks of arriving at Bletchley Park, Turing had specified an electromechanical machine called the bombe, which could break Enigma more effectively than the Polish bomba kryptologiczna, from which its name was derived. The first bombe was installed on 18 March 1940.
The Norway Debate, sometimes called the Narvik Debate, was a momentous debate in the British House of Commons during the Second World War from 7 to 9 May 1940. It has been called the most far-reaching parliamentary debate of the twentieth century. At the end of the second day, the members held a vote of no confidence which was won by the government, but with a drastically reduced majority.
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.
In May, Churchill was still generally unpopular with many Conservatives and probably most of the Labour Party. Chamberlain remained Conservative Party leader until October when ill health forced his resignation. By that time, Churchill had won the doubters over and his successor as party leader was a formality.
His first speech as Prime Minister delivered to the Commons on 13 May was the "blood, toil, tears and sweat" speech. It was 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: I would say to the House... that I have nothing to offer but blood, toil, tears, and sweat. We have before us an ordeal of the most grievous kind. You ask, what is our policy? I will say: it is to wage war, by sea, land, and air, with all our might and with all the strength that God can give us; to wage war against a monstrous tyranny, never surpassed in the dark, lamentable catalog of human crime. That is our policy. You ask, what is our aim? I can answer in one word: it is victory, victory at all costs, victory in spite of all terror, victory, however long and hard the road may be; for without victory, there is no survival.
On 9 June, De Gaulle flew to London and met British Prime Minister Winston Churchill for the first time. It was thought that half a million men could be evacuated to French North Africa, provided the British and French navies and air forces coordinated their efforts.
On the afternoon of Sunday, 16 June de Gaulle was at 10 Downing Street for talks about Jean Monnet's mooted Anglo-French political union. He telephoned Reynaud – they were cut off during the conversation and had to resume later – with the news that the British had agreed.
British Cabinet was reluctant to agree to de Gaulle giving a radio address, as Britain was still in communication with the Pétain government about the fate of the French fleet. Duff Cooper had an advance copy of the text of the address, to which there were no objections.
De Gaulle's Appeal of 18 June exhorted the French people not to be demoralized and to continue to resist the occupation of France. He also – apparently on his own initiative – declared that he would broadcast again the next day.
In his next broadcast on 19 June de Gaulle denied the legitimacy of the government at Bordeaux. He called on the North African troops to live up to the tradition of Bertrand Clausel, Thomas Robert Bugeaud, and Hubert Lyautey by defying orders from Bordeaux. The British Foreign Office protested to Churchill.
On 23 June the British Government denounced the armistice as a breach of the Anglo-French treaty signed in March and stated that they no longer regarded the Bordeaux Government as a fully independent state. They also "took note" of the plan to establish a French National Committee (FNC) in exile, but did not mention de Gaulle by name.
Jean Monnet broke with de Gaulle on 23 June, as he thought his appeal was "too personal" and went too far, and that French opinion would not rally to a man who was seen to be operating from British soil.
On 28 June, after Churchill's envoys had failed to establish contact with the French leaders in North Africa, the British Government recognized de Gaulle as leader of the Free French, despite the reservations of Halifax and Cadogan at the foreign office.
The Battle of Britain began in early July with Luftwaffe attacks on shipping and harbors. The United Kingdom rejected Hitler's ultimatum, and the German air superiority campaign started in August but failed to defeat RAF Fighter Command, forcing the indefinite postponement of the proposed German invasion of Britain. The Battle lasted from 10 July to 31 October.
From 22 July 1940 de Gaulle used 4 Carlton Gardens in central London as his London headquarters. His family had left Brittany (the other ship which left at the same time was sunk) and lived for a time at Petts Wood.
De Gaulle and Churchill reached an agreement on 7 August 1940, that Britain would fund the Free French, with the bill to be settled after the war (the financial agreement was finalized in March 1941). A separate letter guaranteed the territorial integrity of the French Empire.
On 20 August 1940, at the height of the Battle of Britain, Churchill addressed the Commons to outline the war situation. In the middle of this speech, he made a statement that created a famous nickname for the RAF fighter pilots involved in the battle: The gratitude of every home in our Island, in our Empire, and indeed throughout the world, except in the abodes of the guilty, goes out to the British airmen who, undaunted by odds, unwearied in their constant challenge and mortal danger, are turning the tide of the World War by their prowess and by their devotion. Never in the field of human conflict was so much owed by so many to so few.
The Luftwaffe altered its strategy from 7 September 1940 and began to bomb London, at first in daylight raids and then, after their losses became unacceptably high, at night. The raids were soon extended to provincial cities such as the notorious attack on Coventry on 14 November. The Blitz was especially intensive through October and November. It can be said to have continued for eight months, by which time Hitler was ready to launch Operation Barbarossa, the invasion of the USSR. The Luftwaffe failed its objective of reducing British war production, which actually increased. Churchill's morale during the Blitz was generally high and he told his private secretary John Colville in November that he thought the threat of invasion was passed. He was confident that Great Britain could hold its own, given the increase in output, but was realistic about its chances of actually winning the war without American intervention.
On 15 September 1940, known as the Battle of Britain Day, an RAF pilot, Ray Holmes of No. 504 Squadron RAF rammed a German Dornier Do 17 bomber he believed was going to bomb the Palace. Holmes had run out of ammunition and made the quick decision to ram it. Holmes bailed out and the aircraft crashed into the forecourt of London Victoria station.
During the Second World War, the Palace of Westminster was hit by bombs on fourteen separate occasions. One bomb fell into Old Palace Yard on 26 September 1940 and severely damaged the south wall of St Stephen's Porch and the west front.