Why did the US fleet within US littoral waters not take significant defensive action against the U-Boats in 1941/2 despite detailed intelligence from Britain's Enigma deciphering?

  • Even Britain itself rarely took overt action based on the Enigma intelligence, one exempla being sneaking desperately needed supplies to Malta, but only after other attempts had failed repeatedly. In consequence, only in Fall 1944 when planning the Bulge offensive did Hitler demand discontinuance of Enigma, allowing that attack to fully surprise the Allied Command.. – Pieter Geerkens Dec 8 '13 at 13:23

First of all, US was not a belligerent party throughout most of 1941.

Second, the premise is wrong: US did "take significant defensive action in 1941," and arguably offensive ones as well. Although US was not officially at war with Germany, Roosevelt signed an executive order that precluded German warships, including U-Boats, from operating within 1200 miles off US shores, lest US Navy would engage them. This is 100 times further into Atlantic than territorial waters, and contrary to international maritime laws; in fact, Roosevelt wrote to Churchill: "I cannot declare a war, but I can wage a war," referring to US Constitution that precluded him from declaring the war that US Navy was ready to engage in on the West side of the North Atlantic. Because of that German U-Boats had to retreat 1200 miles off US shores and formed a straight line in the middle of North Atlantic.

  • According to one documentary, lights on the Eastern sea-board of the US were merely dimmed (and not turned out), and offensive action was not taken against U-Boats despite the British having full access to U-Boat communications (and supplying this intelligence to the US) and significant US losses due to them, even after the US became a belligerent. Is there any truth in this? – 52d6c6af Dec 8 '13 at 0:10
  • @user3284: I have not heard of any U-Boat attacks directly on US cities, at any time. Once in 1941 a U-Boat sunk a ship heading for England soon after it exited US port as it was entering International Waters, only 12 miles offshore. That prompted Roosevelt extend US patrol well outside US waters, almost 1/2 of the width of the Atlantic. There was no reason to fear U-Boat attack on US cities: a U-Boat could't cross 1200 miles submerged, it would have to surface every 100 miles or so to recharge, and would surely get sunk then. – Michael Dec 8 '13 at 0:22
  • @user3284 lights were dimmed rather than blackouts ordered so as not to alarm the civilian population. As the risk of air attack was zero, there was no perceived need for a blackout (while potentially useful to a submarine commander as an aide in navigation, that was not enough to cause widespread civilian panic). – jwenting Dec 9 '13 at 9:27

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