The exercise model assumed a carrier supported by a fuller destroyer and sloop screen. In wartime, the carrier depended heavily on speed and a single close escort while the other escorts searched outward, exposing the gap between a scored exercise and a submarine attack. Exercise submarines and aircraft also concentrated on high-value battleships because those targets won the exercise, whereas wartime crews would attack any vulnerable enemy ship. Exercises had more often used smaller carriers such as Argus, Hermes, or Eagle; substituting the full-size Courageous magnified the loss without changing the dispersed escort logic. Courageous became both the most valuable and most tempting target in a formation that had sent most of its protection outward to hunt submarines.
Chapter · 1:06:51-1:08:57
Courageous and the limits of anti-submarine exercises
Courageous was lost while carrying out anti-submarine work that peacetime exercises had made look safer and more effective than war proved it to be.