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.
Attacking Allies
Hundreds of defenseless merchant ships were brutally attacked by U-boats. In response, the Allies formed convoys, consisting of up to 200 merchant ships, which were escorted across the Atlantic by escort carriers and destroyers. When a U-boat attacked a convoy, the destroyers launched explosive underwater depth charges and/or hedgehog bombs in an effort to thwart the submerged submarine.
Hitler countered by forming groups of U-boats, called Wolfpacks, to wreak havoc on the convoys. In March 1943, the largest Wolfpack of the war — more than 40 U-boats strong — attacked two convoys made up of 100 Allied ships. Twenty-one merchant ships were sent to the bottom.