Submarines in WWII


Submarines are very valuable attack vehicles. In World War II they were basically surface ships that could travel underwater for a limited time—however, as you will understand after exploring these pages, German U-boats had a number of considerably more advanced features than those of the United States.


Submarines are very large—the hull of the USS Balao (image at left, SS-324 Balao[1]), one of the most successful U.S. submarines and a good example for the basic idea of a submarine, was 312 feet long and displaced 2,415 tons; but also very cumbersome—USS Balao carried 10 officers and 70 enlisted men. High surface velocities and long ranges were attained with strong diesel engines, but these rates were severely reduced underwater, where they relied on electric motors powered by relatively short-lived storage batteries. The USS Balao was powered on the surface by four diesel engines and had a top speed of just over 20 knots (37 km/hr); cruising at 10 knots (18 km/hr) her range was 11,000 nautical miles (20,000 km). Two 126-cell battery groups gave her a submerged top speed of 8.75 knots (16.2 km/hr); holding her speed to 2 knots (4 km/hr), she could remain submerged for 48 hours.   Before sonar became dependable, most submarine combat took place during the day, for the advantage of sunlight (depending on depths). Recharging the batteries usually occurred when combat was more difficult—at night, when the submarine would surface and run the air-breathing diesels.


The main weapon used by submarines is the torpedo, which in itself is a 3,000 pound “mini-submarine,” able to travel about 9,000 yards (a little over 4 miles), and dive and rise through the sea to pre-calculated depths. The submarine can travel with great agility, guided by a gyro and propelled by steam (generated by passing water through burning alcohol). Torpedoes can carry 500 pounds of TNT, to explode either directly upon striking the target or detonated by the influence of the magnetic field of the target’s hull. The USS Balao’s armament included deck guns and 24 torpedoes. The image at left shows a torpedo being deployed.[2]


In comparison to the submarines of the United States, which were already very advanced and won the Pacific theatre, German U-boats displayed greatly enhanced underwater speed and endurance, with highly streamlined hulls and snorkels, and in this way posed one of the most serious risks to the Allied powers in WWII—as will be further discussed. Click below to discover more about the differences between the powers.












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[1] Image source:

[2] Image source: