arrogance...on Doenitz part...u-boat crews suspected this, but because RN and RCN protected and covered up this secret, most sinkings, re-routing of convoys always had an excuse...and Doenitz scoffed at the invisibility of the Enigma as being impregnatabvle...much the same way Rommel believed, and messages by him to OKW where so detailed, when his son was asked about Rommel suspecting this, he said the same, that his father absolutely believed and felt their was no way of his signs being read, and as opposed to other field commanders using sayt land lines, Rommel abstained from this in case taps where placed upon land-lines.....

I think the first ship to succomb to losing the enigma was a weather ship used in the Atlantic, to give advanced notice to the Luftwaffe as to weather conditions, as winds blow from west to east, so to enlighten bomber crews as to expectations on the days weather early in the summer of '40...I think this was taken by a force of British commando's, and the crew abandoned ship, believing it was going to be sunk, and instead boarded...but i could be wrong...

bf109 Emil