Large OPR boats had been designed for Pacific distances, yet wartime shortages sent many into Mediterranean service where many were lost. The S class replaced First World War H-class boats with a medium hull suited to the Mediterranean, North Sea, and North Atlantic. Its balance of range, capability, and construction complexity made it easier to build in numbers than a large ocean-going submarine. Wartime totals vary from 50 to 53 depending on whether completed boats destroyed before commissioning are counted.
Notable Point · 12:11-14:55
Why the S class became Britain's medium submarine
The S class balanced useful range and combat power against the cost and complexity of the larger boats designed for Pacific endurance.