During World War I, U-74 was launched on 10 August 1915, and commissioned into the Kaiserliche Marine on 24 November 1915.
The second U-74 was a Type VIIB submarine of the Kriegsmarine. Her keel was laid down 5 November 1939 by Bremer Vulkan, of Bremen-Vegesack, Germany. She was commissioned 31 October 1940 with Kapitänleutnant Eitel-Friedrich Kentrat in command. Kentrat commanded her until March 1942, when he was relieved by Oberleutnant zur See Karl Friederich, who remained in command until the U-boat's loss.
The U-74 conducted eight patrols, sinking five ships totalling 25,619 tons and damaging two others totalling 11,499 tons.
On 24 May 1941, the German battleship Bismarck and the heavy cruiser Prinz Eugen sank the battlecruiser HMS Hood, and heavily damaged the accompanying battleship HMS Prince of Wales, beginning a three-day battle that would involve nearly a hundred ships.
That concentration of ships was a very attractive set of targets, and Kapitänleutnant Kentrat was ordered to attack the British forces in this area. In the evening U-74 dived in order to listen for contact, and detected another U-boat. Kentrat surfaced and a hundred meters away another U-boat appeared -- U-556, commanded by Kapitänleutnant Wohlfarth.
Earlier, Flottenchef Admiral Lütjens requested that Befehlshaber der Unterseeboote (Commander-in-Chief for Submarines, Karl Dönitz) to provide a U-boat to recover Bismarck's War Diary. BdU had given the order to Wohlfarth, but U-556 was both out of torpedoes and very low on fuel. Using a megaphone, Wohlfarth now passed the order on to Kentrat. Kentrat accepted and proceeded toward Bismarck's last known location.
By dawn on 27 May, Bismarck was crippled and under fire from the battleships HMS Rodney and HMS King George V and the cruisers HMS Norfolk and HMS Dorsetshire. It was clear to her crew that she would not survive.
At 10:36am U-74 heard sinking sounds but could not determine whether it was Bismarck or a British ship. They came to periscope depth and saw battleships and cruisers directly in front of him. He tried to maneuver into an attack position but the weather was too bad and the seas too high to remain on periscope depth or to shoot a torpedo. Wreckage and yellow life-vests were visible.
After the British ships left, Kentrat surfaced amid debris and dead bodies. The sounds they heard that morning was the scuttling of Bismarck. They searched but they could find no one alive until that evening when they rescued a raft carrying three sailors, Georg Herzog, Otto Höntzsch, and Herbert Manthey.
U-74 searched another day but found no one else alive, and was ordered to return to Lorient. On the return trip, the three survivors recovered from their shock and gave the first statements of the end of Bismarck.
U-74 did not suffer any casualties to her crew during her career until 2 May 1942, when she was sunk with all hands (47 men) east of Cartagena by depth charges from a British Catalina aircraft of Squadron 202/C, and from the destroyers HMS Wishart and HMS Wrestler.