According to historian George Donelson Moss, Roosevelt "misled" Americans by reporting the Greer incident as if it would have been an unprovoked German attack on a peaceful American ship.[261] This "shoot on sight" policy effectively declared naval war on Germany and was favored by Americans by a margin of 2-to-1.[262]

Pearl Harbor and declarations of war
See also: Events leading to the attack on Pearl Harbor
Roosevelt and Winston Churchill aboard HMS Prince of Wales for 1941 Atlantic Charter meeting
After the German invasion of Poland, the primary concern of both Roosevelt and his top military staff was on the war in Europe, but Japan also presented foreign policy challenges. Relations with Japan had continually deteriorated since its invasion of Manchuria in 1931, and they had further worsened with Roosevelt's support of China.[263] With the war in Europe occupying the attention of the major colonial powers, Japanese leaders eyed vulnerable colonies such as the Dutch East Indies, French Indochina, and British Malaya.[264] After Roosevelt announced a $100 million loan (equivalent to $1.9 billion in 2021) to China in reaction to Japan's occupation of northern French Indochina, Japan signed the Tripartite Pact with Germany and Italy. 