The lightning Nazi invasion of Soviet Russia on June 22, 1941, altered the course of the war and transformed its character. Overnight, Britain gained a vital partner in arms. Winston Churchill, who had become prime minister on May 10th, reacted on the very afternoon of the unprovoked aggression. He publicly accepted the challenge of a wartime collaboration against the Axis powers and wholeheartedly offered the latest victim all available aid. Churchill's lead in the West to form an alliance with the Soviets at this point unquestionably changed the course of history, heralding Hitler's eventual defeat by the triumph of Allied arms. On July 12, 1941, Great Britain and the Soviet Union signed a pact of nonaggression and mutual assistance, each pledging not to make a separate peace.
The Allied governments-in-exile in London, in particular those of Czechoslovakia and Yugoslavia, soberly understood the parallel commitments, of military cooperation and assistance. The Soviets resumed diplomatic relations with the Czechoslovak government-inexile on July 18th and renewed the suspended treaty of alliance. Now vindicated with the Allied leaders, the Czechoslovak national cause gained significantly in prestige also from British recognition. The British Foreign Office declared that among its war aims were "the restoration of the independence of the Czechs and Slovaks." The Czechoslovak National Committee now became "an organ which handles the affairs of the Czechoslovak refugees and... the Czechoslovak arms... from among the refugees."1
The British had opened their doors to Czechoslovak refugees directly following the Munich Accord, when they had advanced some