First Happy Time

The First Happy Time was a phase of the Battle of the Atlantic during which Germany Navy U-boats enjoyed significant success against the British Royal Navy and its allies. It started in July 1940, almost immediately after France, the United Kingdom's primary ally, was conquered by Germany (the fall of France meant that the German U-boat fleet was brought closer to the British shipping lanes in the Atlantic). When it ended is a matter of interpretation, with some sources claiming October 1940 and others extending it to April, 1941. The reason for this successful German period was the British lack of radar and Huff-Duff equipped ships which meant that the U-boats were very hard to detect when they made nighttime surface attacks (ASDIC [ sonar ] could only detect submerged U-boats).

From July 1940 to the end of October, 282 Allied ships were sunk off the north-west approaches to Ireland for a loss of 1,489,795 tons of merchant shipping.

End of the First Happy Time
Various dates and reasons for the end of the First Happy Time include:
 * March 1941, with the German loss of three prominent U-boat aces: Günther Prien, Joachim Schepke and Otto Kretschmer.