World War II: A German submarine makes the first attack of the war against a United States warship, the USS Greer.

USS Greer (DD–145) was a Wickes-class destroyer in the United States Navy, the first ship named for Rear Admiral James A. Greer (1833–1904). In what became known as the "Greer incident," she became the first US Navy ship to fire on a German ship, three months before the United States officially entered World War II. The incident led President Franklin D. Roosevelt to issue what became known as his "shoot-on-sight" order. Roosevelt publicly confirmed the "shoot on sight" order on 11 September 1941, effectively declaring naval war against Germany and Italy in the Battle of the Atlantic.