Norway recovers 22 mercury containers from Nazi U-boat wreck sunk in 1945

In February 1945, the German U-boat U-864 was sunk off Norway's Fedje island by the British submarine HMS Venturer. This marked the first known instance of one submerged submarine sinking another. The U-864 had been transporting mercury as part of Operation Caesar, a mission to supply Japan's wartime industry.

More than 80 years later, the wreck has become a site of concern due to a potential massive mercury cargo still on the seabed. Norwegian authorities recovered 22 mercury containers from the wreck in June 2026 during an underwater investigation. The Japanese wartime order for the containers, found in British archives, indicated 1,867 containers intended for the U-864, weighing between 65 and 67 tonnes if fully loaded.

However, without surviving loading documents, the exact amount aboard at the time of sinking remains an estimate. The submarine's final mission was to transport specialists, military equipment, and materials to support Japan's wartime industry. Among these was mercury, a strategically important material at the time.

The wreck was discovered in 2003 by the Norwegian Navy's vessel KNM Tyr. Investigations confirmed the submarine had broken into two major sections, with debris scattered around the site. The mercury cargo quickly became the central issue, with Norwegian authorities estimating up to 4 kilograms of mercury leaking from the contaminated area annually.

In June 2026, workers focused on the bow section of the wreck and exposed six keel boxes, finding 22 mercury containers. About 80% of the recovered containers showed damage and leakage. While recovering mercury might seem the straightforward solution, the 2026 operation revealed the challenges. Working around the wreck could disturb contaminated sediment and potentially release mercury into the environment.