T-class boats were ordered from 1935 to replace earlier long-range OPR designs, so the next generation was already under construction when war began. The submarines seen in early wartime service were therefore not necessarily the fleet Britain expected to operate had conflict begun later. Mediterranean experience with the S class and experimental hull work fed into the smaller U class. Wartime construction across these major types reached roughly 150 boats, demonstrating that the Royal Navy maintained a substantial submarine arm alongside its anti-submarine effort.
Notable Point · 16:10-17:45
Interwar replacement plans sustained a large wartime submarine arm
T- and U-class development was already replacing older boats before 1939 and helped Britain build roughly 150 submarines during the war.