Undersea warfare as a contest of anticipated countermoves

The contest resembles multi-level underwater chess because ships and submarines must be designed years before their counters are fully known. Intelligence must anticipate an opponent's present equipment and the tactics and technology likely to appear after the next move. British interwar exercises had already exposed the need for wider depth-charge patterns, forward weapons, and a second escort to maintain contact. The opening of war nevertheless found too few escorts and too few of the preferred theatre-specific submarine classes in service. Wartime experience then revealed false assumptions, such as the belief that a submarine would not surface inside a convoy of supposedly dangerous auxiliaries. Exercise lessons must inform procurement without being mistaken for combat proof.