Few things are more distressing than an overflowing toilet. Aside from the utter revulsion at having one’s home invaded by the toilet’s contents and the need to get it cleaned up as soon as possible, there is the danger of damage to floors, cabinets, and anything (and anyone) that might be on the lower levels.

Despite all of the understandable distress at having to deal with such a calamity in your own home, it is unlikely that any misbehaving toilet ever caused you as much trouble as the one that ended up sinking a state-of-the-art submarine.

As World War II entered into its mid-point, the German navy began work on a new, state-of-the-art submarine. Construction on what would be known as U-1206 began on June 12, 1943, at F. S hi Haru GmbH in Danzig. Less than a year later, on March 16, 1944, the Type VIIC U-boat went into service. After completing its trial runs, it began its first active patrol on April 6 under the command of Kapitänleutnant Karl-Adolf Schlitt.

Among the new features of U-1206 was a deepwater high-pressure toilet. The innovation allowed the toilet to be flushed while the submarine was submerged, but it was not as simple as pushing a lever on the side of the tank. The use required the assistance of specially-trained technicians.

Hmmm…. In retrospect, that last sentence could use some clarification. The actual use of the commode required little training beyond that provided by parents during a child’s formative years. What was complicated was the flushing.

Learning how to flush a toilet can be an elusive skill, frequently forgotten by teenage boys and not relearned until after they get married. Flushing the toilets on U-1206 was even more complex than that, however. The toilet’s mechanisms involved a number of intersecting tubes with valves that had to be opened and closed in the correct sequence. Getting it wrong meant a lot more than having to clean up the bathroom floor — it resulted in seawater flooding into the submarine.

On April 14, 1945 — eight days into U-1206’s first patrol and 24 days before the end of World War II in Europe — the submarine was cruising at a depth of 200 feet (61 m), eight nautical miles (15 km; 9.2 mi) off Peterhead, Scotland. Someone flushed the toilet incorrectly. Massive amounts of the North Sea made their way into U-1206. Before they could get the stool under control, the submarine’s batteries were flooded. They were, inconveniently, located directly below the bathroom. The introduction of seawater to the batteries triggered a cloud of chlorine gas that threatened to poison the entire crew.

Left with no other choice, the commanding officer ordered U-1206 to surface. They could not have picked a worse location. Immediately upon surfacing, the ship was spotted by British patrols and came under heavy fire. The submarine was so badly damaged that Kapitänleutnant Schlitt was forced to scuttle the submarine.

U-1206 sank to the bottom of the North Sea, having served eight days on active patrol. One sailor was killed during the attack, and three others drowned after abandoning the vessel. Forty-six men were captured by the British.

All things considered, that toilet ended up being one of the deadlier weapons of the war.