In general, by torpedoing their enemy's ships. Missile-carrying submarines may be loaded with either nuclear- or conventional- warhead missiles; and carry torpedoes. Conventional submarines are armed only with torpedoes; and some modern types are designed primarily to seek and sink enemy submarines. In WW2 the German U-boats hunted in "wolf-packs" to destroy Allied merchant shipping in convoys across the N.Atlantic. One even managed to creep into the St. Laurence seaway and sink a ship there - former U-boat officers have remarked that the Americans at the time had no concept of black-out precautions, making their task a lot easier. The U-boat attacks on convoys stopped only when advances in anti-submarine warfare raised the attrition rate for the Germans to an unacceptable level. The Nazi's Enigma code machine found by the Royal Navy was the one fitted to a captured U-boat; but most U-boat losses were by sinking by depth-charges.
No, not really, submarines were first used successfully in the Civil War.
Why don't you just Google "World War 1 Submarines?"
Submarines changed war. They played a big part of World War I and II.
Yes, submarines were used by the Confederate Navy in the US Civil War.
World War I submarines were primarily used to locate and attack surface cargo and warships.
Submarines were sometimes referred to as submersibles.
Argentina had diesel-electric submarines while the British had nuclear-powered submarines.
David Bushnell invented the first war submarine
Yes
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The submarines were either called "submarines" or "U-boats." The German submarine was called the "U-boat"
2,200,000 Soldiers 97 Warships 40 Submarines.