USS Greer attacks U-boat in Atlantic
4th September 1941: First open act of force by US against Germany
The escalation of tension between Germany and the United States was almost inevitable as the US provided ever closer assistance to the Royal Navy in the Battle of the Atlantic. The facts of the 'Greer incident' - when the U 652 unsuccessfully attempted to torpedo the USS Greer and was then herself subjected to an unsuccessful depth charge attack were subject to some interpretation by both sides.
In his ‘fireside chat’ radio address to the American public on the 11th September President Roosevelt was to state:
The Greer was flying the American flag. Her identity as an American ship was unmistakable. She was then and there attacked by a submarine. Germany admits that it was a German submarine. The submarine deliberately fired a torpedo at the Greer, followed by another torpedo attack.
In spite of what Hitler's propaganda bureau has invented, and in spite of what any American obstructionist organisation may prefer to believe, I tell you the blunt fact that the German submarine fired first upon this American destroyer without warning, and with the deliberate design to sink her.1
‘if German or Italian vessels of war enter the waters, the protection of which is necessary for American defense, they do so at their own peril’
As a direct consequence Roosevelt announced what became known as his "shoot-on-sight" order:
The aggression is not ours. [Our concern] is solely defense. But let this warning be clear. From now on, if German or Italian vessels of war enter the waters, the protection of which is necessary for American defense, they do so at their own peril. . . . The sole responsibility rests upon Germany. There will be no shooting unless Germany continues to seek it.
However Roosevelts account of the incident did not quite tell the whole story. It was some time later that Admiral Stark provided a full account of the incident after the Senate Committee on Naval Affairs looked into the matter:
At 0840 that morning, Greer, carrying mail and passengers to Iceland, "was informed by a British plane of the presence of a submerged submarine about 10 miles [(16 km)] directly ahead. . . . Acting on the information from the British plane the Greer proceeded to search for the submarine and at 0920 she located the submarine directly ahead by her underwater sound equipment.
The Greer proceeded then to trail the submarine and broadcasted the submarine's position. This action, taken by the Greer, was in accordance with her orders, that is, to give out information but not to attack."The British plane continued in the vicinity of the submarine until 1032, but prior to her departure the plane dropped four depth charges in the vicinity of the submarine. The Greer maintained [its] contact until about 1248. During this period (three hours 28 minutes),the Greer maneuvered so as to keep the submarine ahead.
At 1240 the submarine changed course and closed the Greer. At 1245 an impulse bubble (indicating the discharge of a torpedo by the submarine) was sighted close aboard the Greer. At 1249 a torpedo track was sighted crossing the wake of the ship from starboard to port, distant about 100 yards [(100 m)] astern. At this time the Greer lost sound contact with the submarine.
At 1300 the Greer started searching for the submarine and at 1512 . . . the Greer made underwater contact with a submarine. The Greer attacked immediately with depth charges.
https://millercenter.org/the-presidency/presidential-speeches/september-11-1941-fireside-chat-18-greer-incident