Winston Churchill announced during a speech at Mansion House in London, “If Japan makes war on the United States; Great Britain will support America within the hour.”

Source: “War May Engulf Remaining Fourth of Globe, Churchill Declares; Nazis Strike Anew at Leningrad.” The Ithaca Journal, 10 Nov. 1941, p. 1. https://www.newspapers.com/article/the-ithaca-journal/134522574/