The submarine war commenced on the third day of the conflict when a German submarine, U-30, commanded by Lieutenant Fritz Julius Lemp, engaged in a fire on the British passenger liner Athenia. The Athenia subsequently sank the following day, with the majority of its passengers being rescued. Tragically, 112 individuals lost their lives, including 28 Americans. Notably, Lemp disregarded explicit orders prohibiting the firing of on passenger vessels. During the initial four months of the war, a staggering 221 vessels, surpassing 750,000 tons in total tonnage, were sunk.

On the evening of September 17, German U-boat 29, under the command of Commander Otto Schuart, launched three torpedoes at the HMS Courageous. Within a mere fifteen minutes, the Courageous sank, taking with it its captain and 518 men.

On October 13th, Lieutenant Gunter Prien, commanding U-boat 47, successfully maneuvered into the British naval base at Scapa Flow. There, he executed a daring attack on the British battleship Royal Oak. Initially, Prien fired four torpedoes at the battleship, resulting in only one hit that caused significant damage above the waterline. Undeterred, Prien returned to fire three additional torpedoes. One of these torpedoes detonated in a catastrophic manner, leading to the sinking of the Royal Oak and the loss of 833 lives within fifteen minutes.

The period between July and October 1940 is commonly referred to as the “Happy Time” for German submarines. During this period, the wolf pact, a collaborative operation involving multiple submarines operating in convoys, became operational. U-boats achieved an exceptional record of sinking 217 ships, representing over a million tons of shipping, while sustaining only six losses. 

In 1941, the tide of U-Boat activities experienced a temporary shift. The implementation of additional escorts, air patrols, and the US convoying of ships across the Atlantic significantly reduced U-Boat losses. However, the period following the American entry into the war temporarily reversed this trend. Suddenly, hundreds of unescorted vessels were off the coasts of the US, elegantly silhouetted against the lights of US cities.

By early 1943, the tide decisively turned against the U-Boats. The Allies had 500 escorts at their disposal, intercepting U-Boat radio communications. The introduction of escort carriers enabled uninterrupted air coverage for convoys across the Atlantic. Consequently, by mid-1944, one U-Boat was being lost for every Allied ship sunk. The war in the Atlantic persisted, but victory was firmly within the grasp of the Allies.

By the conclusion of the war, the U-Boats had sunk 3,500 merchant vessels, resulting in the loss of 36,000 merchant seamen. Additionally, they sank 175 warships, with the loss of life amounting to 36,200 sailors. Notably, 783 U-Boats were sunk, claiming the lives of 30,000 German sailors.

List of Sunk U-boats