U-boat comes from the German word unterseeboot. It is the basic German diesel-electric submarine that changed submarine warfare during World War II. U-boats constructed during World War II were Type VII-C. It was made of steel and displaced 871 metric tons of water, which is only a tenth of the modern ones produced by the U.S. today. It could hold only 14 torpedoes in its bow and stern compartments, and like all U-boats, it depended on its rechargeable batteries to operate while submerged. When a U-boat surfaced, it used its air-breathing diesel engine to propel itself and to recharge its batteries.
The principal weapon of the U-boats was the torpedo. During World War IIGerman submarines used torpedoes powered by compressed air, and later used electric models that left no sign of bubbles. An 88-mm naval deck gun was used for surface combat. This was used frequently to finish off torpedoed ships or to attack smaller vessels.
Most U-boats also had antiaircraft guns mounted behind the conning tower.
Early in World War II, U-boats individually patrolled regional areas looking for targets, but Germany eventually embraced the "wolf pack" strategy of sending groups of submarines to confront enemy convoys.
Germany began World War II with fewer than 100 U-boats, but produced several thousand between 1939 and 1945. Several factors credit for the defeat of the U-boat campaign including the development of sonar to pinpoint their locations. About 40,000 members of the U-boat service fought for the Nazi Germany during six years of war. Only 12,000 men survived. Germany lost 784 U-boats to Allied attacks, but the Allies lost more than 2800 merchant ships to the submarines.