The Japanese surprise attack on the Pacific Fleet at Pearl Harbor on December 7, 1941, brought America into the war. Churchill was with the President's special envoy, Averell Harriman, and the U.S. Ambassador to Britain, John Gilbert Winant, when he received the news over the telephone from President Roosevelt.

Four days later, Germany declared war on the United States, making U.S. involvement in Europe inevitable. Churchill was eager to have the U.S. fight alongside the British forces in Europe and wasted no time. He undertook a dangerous transatlantic journey on the HMS Duke of York, arriving in America on December 22, in time to spend Christmas at the White House.

On December 26, Churchill made his first historic address to a joint session of Congress to win support for his concept of the war. In public, he seemed to epitomize the “bulldog” fighting spirit. In private, the strain was taking its toll, and that very evening Churchill suffered a mild heart attack.