Highest death toll from a single ship disaster during wartime

The deadliest maritime disaster in wartime, and the deadliest overall, was the sinking of the MV Wilhelm Gustloff, a German military transport ship. It was torpedoed during the Nazi evacuation of military personnel and civilians from East Prussia in the last months of World War II. The ship's manifest said there were 6,050 people on board, but post-war researchers have suggested that the actual number may have been as high as 10,500. A few hours after the Wilhelm Gustloff's departure from Gotenhafen (present-day Gdynia) on 30 January 1945, the Soviet submarine S-13 fired a salvo of three torpedoes into the ship's port side. A total of 1,252 people were rescued from the rapidly sinking ship, which means the death toll was somewhere between 4,798 and around 9,400 people.

The Wilhelm Gustloff was originally built as a cruise liner, to be operated as part of the Nazi Party's "Strength Through Joy" subsidized tourism and leisure scheme. It was going to be named the MV Adolf Hitler, but this was changed to memorialize the assassinated leader of the Swiss Nazi Party shortly before its launch. The Wilhelm Gustloff made its maiden voyage in March 1938, but only served as a civilian cruise ship for about a year and a half before being requisitioned by the military, first as a hospital ship and later a military transport. It was used in support of the German invasion of Norway and was earmarked for use in the abandoned Operation Sealion (the invasion of Britain).

At the time of its sinking, the Wilhelm Gustloff was taking part in Operation Hannibal, the evacuation of the German territory of East Prussia (which covered present-day northeastern Poland and Russia's Kaliningrad Oblast), which had been encircled by Soviet forces in early January 1945. Priority was given to German military personnel, Nazi officials and civilian government employees, but each ship that left the ports of East Prussia was typically also loaded with thousands of civilian refugees, fleeing the advancing Red Army.

Some accounts of this disaster describe the Wilhelm Gustloff as a hospital ship or a civilian vessel, but this was not true at the time of the sinking. As the ships involved in Operation Hannibal were under Navy command, armed with anti-aircraft weapons, and tasked with evacuating military personnel and equipment, they would not have been considered non-combatant or hospital ships under international law. Leaving Gotenhafen, Wilhelm Gustloff was painted the same grey as other German Navy (Kriegsmarine) vessels and had no red cross markings; it flew the Kriegsmarine flag; and it was accompanied by an escort of Navy destroyers.

The commanders of the Wilhelm Gustloff were aware of the danger they were running in their final voyage. As the ship was leaving port, they had to make the fateful choice on whether to stick to shallow coastal waters – where they would be safe from submarine attack, but at risk of striking a mine – or venture across the deep-water route that had been cleared of mines, but was patrolled by Soviet submarines. They chose the latter, and soon after departure they were spotted in the early evening by the crew of Soviet submarine S-13, commanded by Alexander Marinesko.

At around 9 p.m., long after night had fallen and the temperatures had dropped to around -18 C, the S-13 fired four torpedoes at the ship's port side. One failed to detonate, but the others struck the ship. The first hit the bow below the waterline, the second struck amidships, and the last struck near the stern, destroying the ship's engines. These three massive explosions left the vessel with no power and a rapidly worsening list to port.

Few passengers were able to get off the massively overcrowded ship, which was tipping over at an increasingly precarious angle and plunged into complete darkness by the destruction of the engines and electrical generators. The ship had nowhere near enough lifeboats for the number of people on board, and as it tipped over it became impossible to launch the boats on the starboard side. Many passengers went down with the ship, and most of those who jumped froze to death before they could be recovered by one of the rescue ships.