S-class submarines offered a medium design suited to the Mediterranean, North Sea, and North Atlantic, while River-class fleet submarines explored boats able to operate with the battle fleet. Medium boats offered a balance of range, capability, and construction complexity that very large ocean-going submarines could not match. The Navy also retained an interest in submarine mine-laying after First World War experience. T-class orders from 1935 show that replacement and expansion plans were already under way before the next war began.
Chapter · 12:11-17:45
S, River, mine-laying, and T-class submarine roles
The interwar force combined medium boats, fleet submarines, mine-layers, and the T class rather than relying on one standard type.