Hemispheric Defense Zone - U.S. still officially neutral, Roosevelt declared the entire western half of the Atlantic was part of the Western Hemisphere and therefore also neutral. He then ordered the U.S. Navy to patrol the western Atlantic and reveal the location of German submarines to the British.
Pearl Harbor - Japan’s surprise attack on the U.S., December 7, 1941. Eight battleships, three cruisers, three destroyers, and four other vessels were sunk or damaged. The attack destroyed over 180 aircraft and killed 2,403 Americans. Another 1,178 were injured.