Asdic contact and coordinated depth-charge attacks

Interwar exercises often counted an Asdic contact as a successful attack without following the problem through to a depth-charge run. In action, the attacking ship tended to lose contact as it closed to dropping range, giving the submarine a chance to evade. Escort groups adapted in 1940 and 1941 by working in pairs or threes. One ship maintained the Asdic track while the others attacked, and they changed roles as needed. The tracking ship's assistance deserved as much credit as the attack itself because the roles were interchangeable and both were necessary. The exercise standard had hidden the point at which a real attack failed, so training and tactics both had to change.