The U-Boat Menace:
Attacking Merchant Ships
U-boats were designed to spend most of their time above water, where lookouts scanned the horizon for telltale smoke from merchant ship smokestacks. Once a ship was spotted, the captain submerged his U-boat and stalked his prey using a periscope to peer above the waves. When the captain shouted "Fire One!" the U-boat crew launched a torpedo toward the doomed ship.
Seconds later, the torpedo would explode violently into the merchant ship, ripping a jagged hole in its hull. Seawater flooded in, as fires started secondary explosions that rocked the ship. Crewmembers ran for their lives, trying to abandon ship before being dragged to the bottom of the icy sea. Most didn't survive.
Allied Ships Sunk by U-boats
in the Atlantic Ocean
As the war progressed, the Allied supply lines were constantly under attack, until the development of Hunter-Killer Task Groups. These groups helped protect the convoys by simply hunting down menacing U-boats. By the end of the war our convoys were cruising the waters without fear. The chart below shows just how many Allied ships were sunk compared to the number of U-boats sunk in the Atlantic Ocean.