Exercises taught lessons but also created blind spots

Peacetime results could never provide a complete forecast of war. Mediterranean exercises offered predictable weather, deep water, and valuable opportunities to assemble carriers, destroyers, submarines, and aircraft. One exercise concentrated four of the Royal Navy's six carriers, while another annual practice reached five, a concentration a multi-theatre war might not permit. Those conditions did not reproduce every North Atlantic or Pacific current, thermal layer, shallow-water problem, or operational pressure. Using armed fleet auxiliaries as simulated merchantmen also discouraged the surfaced attacks inside a convoy that U-boats later attempted against unarmed shipping. Wartime WRENs and officers used tactical analysis and wargaming to expose that faulty assumption after combat revealed it. Technology and tactics must be studied through exercises and combat history because performance and opponent behaviour rarely arrive exactly as advertised.