The British Submarines That Sank 412,000 Tons In Waters Germans Couldn't Enter

May 24, 1941. HMS Upholder, waters 130 feet deep. German U-boats needed 200+ feet minimum. Italian submarines needed even deeper.
Lieutenant Commander Wanklyn fired two torpedoes. Conte Rosso (17,879 tons) sank. Thirty-seven depth charges followed. Upholder survived at 120 feet—10 feet off the bottom.
Originally designed as training boats, U-class submarines operated in Mediterranean shallows where larger German and Italian submarines couldn't follow. 12 submarines maximum sank 412,575 tons of Axis shipping (January 1941 - December 1942).
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THE ADVANTAGE:
German Type VII: 871 tons, needed 200+ feet depth
British U-class: 730 tons, operated in 100-foot waters
30-second crash dive vs 45-second German
Mediterranean coastal waters: 100-300 feet average
Germans physically couldn't operate there
British dominated shallows
ACHIEVEMENT:

412,575 tons sunk (12 submarines, 18 months)
HMS Upholder: 93,031 tons in 11 months
HMS Urge: 74,000 tons, damaged battleship
Italian sonar classified them as "rocks and wrecks"

SHALLOW WATER TACTICS:

Bottom-sitting: landed on seabed, zero noise
30-second crash dive (vs German 45 seconds)
Silent running: Italian destroyers couldn't detect motionless subs

ENEMY RESPONSE:
German records: "repeated route changes"
Italian submarines: 3 lost to grounding trying to copy British tactics
Axis convoys: forced to longer deep-water routes
Script: "Rommel's Afrika Korps suffered critical supply shortages directly attributable to submarine interdiction."

THE LESSON:
Germans had bigger submarines (871 tons vs 730 tons). British had depth capability (100 feet vs 200+ feet). Mediterranean shallows favored British. 412,000 tons proves it.

Training boats operated where combat U-boats couldn't. Smaller = advantage in shallow seas. 12 submarines strangled Rommel's supply lines.

Sources: Royal Navy Submarine Records, Malta Flotilla Reports, Axis Loss Records

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© British Naval History. How training boats in 100-foot waters sank 412,000 tons Germans couldn't reach.