Germany was the United Kingdom's primary threat, especially after the
Fall of France in 1940, which saw Germany overrun most of the countries of Western Europe, leaving the United Kingdom alone to combat Germany. Germany's threatened invasion of the UK,
Operation Sea Lion, was averted by its failure to establish air superiority in the
Battle of Britain, and by its marked inferiority in naval power. At the same time, war with Japan in East Asia seemed increasingly likely. Although the U.S. was not yet at war, it met with the UK on several occasions to formulate joint strategies. In the March 29, 1941 report of the
ABC-1 conference, the Americans and British agreed that their strategic objectives were: (1) "The early defeat of Germany as the predominant member of the
Axis with the principal military effort of the United States being exerted in the Atlantic and European area;" and (2) "A strategic defensive in the Far East." Thus, the Americans concurred with the British in the grand strategy of "Europe first" (or "Germany first") in carrying out military operations in World War II. The UK feared that, if the United States was diverted from its main focus in Europe to the Pacific (Japan),
Hitler might crush the Soviet Union, and would then become an unconquerable fortress in Europe. The wound inflicted on the United States by
Japan's attack on the US at Pearl Harbor on December 7, 1941, did not result in a change in U.S. policy. Churchill hastened to Washington shortly after Pearl Harbor for the
Arcadia Conference to ensure that the Americans didn't have second thoughts about Europe First. In 1941, Roosevelt appointed
John Gilbert Winant ambassador to Britain, and Winant remained in that post until he resigned in March 1946. In a 2010 book,
Citizens of London: The Americans Who Stood with Britain in Its Darkest, Finest Hour, author
Lynne Olson described Winant as dramatically changing the U.S. stance as ambassador when succeeding pro-appeasement ambassador
Joseph P. Kennedy Sr. In the spring of 1941,
W. Averell Harriman served President Franklin D. Roosevelt as a special envoy to Europe and helped coordinate the
Lend-Lease program. The two countries reaffirmed that, "notwithstanding the entry of Japan into the War, our view remains that Germany is still the prime enemy and her defeat is the key to victory. Once Germany is defeated the collapse of Italy and the defeat of Japan must follow." ==United States==