The most common U-boat attack during the early years of the war was conducted on the surface and at night, see submarine warfare.

The convoy came under heavy air and U-boat attack, sustaining high losses.

They were shipped across the Atlantic and survived potential loss by U-boat attack.

No. 269 ircraft made eight separate U-boat attacks during August.

I ran statistical analyses of convoy sinkings and U-boat attacks.

The signals were picked up by the convoy's escorts; and, that night, they drove off the first U-boat attack.

In common with many merchants, she travelled in convoys to protect against the risk of a U-boat attack.

During the voyage the Dunera narrowly survived another U-boat attack.

In the meanwhile the ships of PQ 13 came under U-boat attack.

Nine ships were lost to German U-boat attacks near Greenland.