4 September 1941
During a convoy operation the US destroyer Greer is attacked by a German U-Boat.
It is not damaged and in return the destroyer attempts to sink the submarine with depth charges. In fact the Greer has been brought into action by reports of a British aircraft and has been mistaken, not unreasonably, for a British ship by the Germans. Roosevelt presents the incident to the American public as an example of Nazi aggression.
This incident leads to President Roosevelt to issue what became known as his “shoot-on-sight” order.