Victor,

Thanks for your answer.

Conditions were as follows: Calm sea, little wind. Partial moon, mostly clear, perhaps a cloud or two.

The time was just before midnight, Dec 26-27, 1944. The convoy was bound for Cardiff, Wales. I suspect the conditions were rather ideal for the u-boat to try a surface attack?

I realize that being on the surface day or night was very dangerous for u-boats, because of the allied air umbrella (patrolling aircraft) over the region.

Incidentally, the Battle of the Bulge was underway on the continent.