Warfare, took political responsibility for the SOE and recorded in his diary that Churchill told him: "And now go and set Europe ablaze". The Battle of Britain and the Blitz 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 Luftwaffe altered its strategy from 7 September 1940 and began the Blitz, which was especially intensive through October and November. 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 past. 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. Lend-Lease In September 1940, the British and American governments concluded the Destroyers for Bases Agreement, by which fifty American destroyers were transferred to the Royal Navy in exchange for free US base rights in Bermuda, the Caribbean and Newfoundland. An added advantage for Britain was that its military assets in those bases could be redeployed elsewhere. Churchill's good relations with United States President Franklin D. Roosevelt helped secure vital food, oil and munitions via the North Atlantic shipping routes. It was for this reason that Churchill was relieved when Roosevelt was re-elected in 1940. Upon re-election, Roosevelt set about implementing a new method of providing necessities to Great Britain without the need for monetary payment. He persuaded Congress that repayment for this immensely costly service would take the form of defending the US. The policy was known as Lend-Lease and it was formally enacted on 11 March 1941. Operation Barbarossa Hitler launched his invasion of the Soviet Union on Sunday, 22 June 1941. It was no surprise to Churchill, who had known since early April, from Enigma decrypts at Bletchley Park, that the attack was imminent. He had tried to warn General Secretary Joseph Stalin via the British ambassador to Moscow, Stafford Cripps, but to no avail as Stalin did not trust Churchill. The night before the attack, already intending an address to the nation, Churchill alluded to his hitherto anti-communist views by saying to Colville: "If Hitler invaded Hell, I would at least make a favourable reference