2. The German declaration of war on the United States on December 11, 1941, in response to the U.S. declaration of war on Japan following the attack on Pearl Harbor.
3. The Battle of the Atlantic, a series of naval engagements that took place in the Atlantic Ocean between Allied and German forces from 1939 to 1945, in which the U.S. Navy played a significant role in protecting Allied shipping lanes and countering German U-boats.