Unterseeboot 864

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U-864
Type		IXD
Commission Date		9 December 1943
Construction yard		AG Weser, Bremen
Patrols
Start Date	End Date	Assigned Unit
5 December 1944	9 February 1945	33rd Flotilla
Commanders
9 December 1943	9 February 1945	Korvkpt. Ralf-Reimar Wolfram
Successes
Type of Ship Sunk	Number of Ships Sunk	Gross Registered Tonnage
Commercial Vessels	None	0
Military Vessels	None	0

Unterseeboot 864 (U-864) was a German Type IX U-boat sunk on February 9, 1945 by the British submarine HMS Venturer, killing all 73 onboard. It is the first instance in the history of naval warfare that one submarine sank another while both were submerged. The shipwreck was located in March 2003 by the Royal Norwegian Navy 2.2 miles west of the island of Fedje in the North Sea, at 150 metres.^[1]

Contents 1 Career 1.1 Early career 1.2 Operation Caesar 2 Rediscovery 3 References

[edit] Career

[edit] Early career

Commanded throughout its entire career by Korvettenkapitän Ralf-Reimar Wolfram ^[2], she served with the 4th Submarine Flotilla (4 Unterseebootflottille) undergoing crew training from her commissioning until 31 October 1944. She was then reassigned to the 33rd Submarine Flotilla (33. Unterseebootflottille).^[3]

[edit] Operation Caesar

The submarine was taking part in Operation Caesar, an attempt by Germany to prop up their flagging Japanese ally by providing them with advanced technology, and en route from Kiel to Japan with plans for the Messerschmitt Me 262 jet fighter,^[4] jet engine parts, about 65 tons of metallic mercury and German and Japanese scientists and engineers.^[5]

She set off through the Kiel Canal but grounded on the sea bed and had to make an unscheduled stop at the Bruno U-boat pens at Bergen. The crew left on shore leave, which lasted longer than expected after the pens and shipping in the harbour were attacked on 12 January by 32 Royal Air Force Lancaster bombers and one Mosquito bomber of Numbers 9 and 617 Squadrons. At least one of the Tallboy bombs penetrated the roof of the bunker causing severe damage inside, and leaving one of the seven pens unusable for the rest of the war.^{[6] [7]} Cryptographers at Bletchley Park had already learned of the plan.

British submarine HMS Venturer (commander, Lieutenant James "Jimmy" S. Launders, 25) was sent on her eleventh patrol from the British submarine base at Lerwick in the Shetland Islands out to Fedje. After the U864 messages had been decrypted, she was rerouted to intercept the U-boat. The U-boat meanwhile had left Bergen, and on February 6 passed the Fedje area without being detected, but despite repairs at Bergen one of her engines began to misfire and she had to signal that she would again return to Bergen. A return signal stated that a new escort would be provided her at Hellisoy on 10 February. She made for there but on 9 February Venturer heard U-864's engine noise (Launders had decided not to use ASDIC since it would betray his position) and spotted the U-boat's periscope.

In an unusually long engagement for a submarine and in a situation for which neither crew had been trained, Launders waited 45 minutes after first contact before going to action stations, waiting in vain for U864 to surface and thus present an easier target. Upon realizing they were being followed by the British submarine and that their escort had still not arrived, U-864 zig-zagged in attempted evasive manoeuvres and each submarine risked raising her periscope. Venturer had only 4 torpedoes as opposed to U-864's 22, and so after 3 hours Launders decided to make a prediction of his opponent's zig-zag, and release a spread of his torpedoes into its predicted course. The first torpedo was released at 12:12 and then at 17 second intervals after that (taking 4 minutes to reach their target), and Launders then dived suddenly to evade any retaliation from his opponent. U864 heard the torpedoes coming and also dived deeper and turned away to avoid them, managing to avoid the first three but unknowingly steering into the path of the fourth. Exploding, she split in two, was sunk with all hands and came to rest more than 150 m (500 ft) below the surface on the seafloor.

The encounter between the U-864 and HMS Venturer was the subject of a Timewatch documentary on BBC Television broadcast on 5 January 2007. The programme switched between a reconstruction of the confrontation between the two submarines and a fly on the wall style documentary about a Norwegian vessel analysing the wreckage of the U-864.^[8]

[edit] Rediscovery

In early 2003, the Royal Norwegian Navy, alerted by local fishermen, found the wreck. The mercury, contained in 1,857 rusting steel bottles located down in the vessel's keel, has started to leak and currently poses a severe environmental threat (see mercury poisoning and Minamata disease).

So far 4 kilograms per year of mercury is leaking out into the surrounding environment, resulting in high levels of contamination in cod, torsk and edible crab around the wreck.^[9] Boating and fishing near the wreck has been prohibited. Although attempts using robotic vehicles to dig into the half-buried keel were abandoned after the unstable wreck shifted, one of the steel bottles was recovered. Its original 5 mm thick wall was found to have corroded badly, leaving in places only a 1 mm thickness of steel.^[10]

The delicate condition of the 2,400-ton wreck, the rusting mercury bottles, and the live torpedoes on board would make a lifting operation extremely dangerous, with significant potential for an environmental catastrophe.^[10][11] A three year study by the Norwegian Coastal Administration has recommended entombing the wreck in a 12 metre thickness of sand, with a reinforcing layer of gravel or concrete to prevent erosion. This is being proposed as a permanent solution to the problem, and the proposal notes that similar techniques have been successfully used around 30 times to contain mercury-contaminated sites over the past 20 years. ^[12]

[edit] References

Coordinates: 60°46′10″N, 4°37′15″E