"The only thing that ever really frightened me during the war was the U-boat peril," British Prime Minister Winston Churchill reportedly said while reflecting on the second world war.
By the end of the war, Hitler's Kriegsmarine, the navy of Nazi Germany, had built 1,162 U-boats, which is short for the German word "Unterseeboot," or undersea boat.
In the fall 2015 issue of Weapons of WWII magazine, Marc DeSantis explains how the U-boats were used during World War II.
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At the beginning of the war, the commander of the German U-boat fleet, Karl Dönitz, said that if he had 300 U-boats, "he could strangle Britain and win the war."
Source: Weapons of WWII magazine
The Kriegsmarine began the war with just 56 U-boats, but over the course of the war they would build 691 type VII U-boats alone. Here's a photo of a U-35 boat during training exercises in 1936.
Source: Weapons of WWII magazine
The U-boat was not a true submarine in today's sense of the word. It was more of a submersible craft. The diesel engines required air, so while underwater, the craft was powered by 100 tons of lead-acid batteries, meaning it had to surface every few hours when air and battery power were exhausted.
Source: Weapons of WWII magazine
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