when did us enter ww2

The United States officially entered World War II on December 8, 1941, the day after Japan's surprise attack on the U.S. naval base at Pearl Harbor on December 7, 1941. Following this attack, which President Franklin D. Roosevelt called "a date which will live in infamy," the U.S. declared war on Japan. Subsequently, Germany and Italy declared war on the United States on December 11, 1941, which brought the U.S. into the broader global conflict on both the Pacific and European fronts.