Convoy-interior attacks and doctrine adaptation

Surface speed let U-boats keep up with merchant shipping, but escorts made an exposed surface approach dangerous. Early in the war, commanders exploited the assumption that protection would remain around the convoy perimeter and attacked from inside the formation. Once the Royal Navy recognized the tactic, it adapted by keeping an escort within the convoy, illustrating wartime doctrine changing through operational evidence. The correctable flaw fits the larger conclusion that Britain had convoy ideas and capabilities but could not complete its preparations before war arrived.