German weather ship Lauenburg

The former trawler Lauenburg was under the name WBS 3, a weather observation ship ( WBS) of the German Navy in World War II. The ship was named after the northern German town of Lauenburg. The weather observation ships had the task of providing weather reports to the German Naval Command, and especially for commercial belligerent submarines.

With the hijacking and subsequent sinking of Lauenburg on 28 June 1941, the Royal Navy managed to bring major German code books and instructions on setting the Enigma cipher machine in their possession.

Early Career

The Lauenburg ( identification number PG 532) was on July 1, 1936 specified in Kiel, and in 1938 finished trawlers fishing Bremer H. Bischoff & Co., who operated from the home port Geestemünde. In 1940 the ship was commandeered by the Navy and, after appropriate modification, put into service in November 1940 as a weather observation ship 3 (WBS 3). The crew consisted now of 19-21 men and eight meteorologists.

The weather observation ships and the Enigma

The working at Bletchley Park British cryptanalyst Harry Hinsley came in April 1941 at the conviction that the German Wetterbeobachtungssschiffe that were unarmed and alone at their positions, the same Enigma machines and codebooks used as the German submarines. Although the WBS not encrypted their weather reports with the Enigma, but they needed the codes to decipher radio messages addressed to it. Could the code book from one of these WBS capture, so you would be able to decipher the Enigma code of the Navy and thus to read radio messages to submarines and submarines and to determine their positions. Although one had to assume that the crew of an attacked WBS would throw the currently valid Enigma settings and codes overboard believed Hinsley that the settings for the following month probably enclosed in a safe and would left behind by the crew there when this would be forced to quickly leave their ship.

The British Admiralty was convinced and sent beginning in May 1941 seven cruisers and destroyers in the sea area north-east of Iceland, where the destroyer HMS Somali on May 7, the weather observation ship Munich kaperte and thereby captured the Enigma settings for the month of June. So that the marine radio messages were decrypted in June very quickly.

When the German Naval Command in mid-June auswechselte the Enigma used in the bigram tables, it was necessary for the Royal Navy to capture the new code. Although it was aware of the risk that the predation of another Wetterbeobachtungssschiffs within such a short time could indicate the German Naval Command on this vulnerability, were on 25 June 1941, the light cruiser HMS Nigeria and the destroyer HMS Tartar, HMS Jupiter and HMS Bedouin of Scapa Flow set out on the march to conquer the Jan Mayen positioned in the marine WBS Lauenburg. On the march to the north of the commander of the Tartar instructed his artillery boatswain that he Lauenburg meet under any circumstances, but only should move their occupation to hasty as possible leaving their ship.

The hijacking of Lauenburg

The Lauenburg left Trondheim on May 27, 1941 Course on their area of ​​operation OG 3 northeast of Jan Mayen. On June 2, she started sending their weather reports from the naval grid square FROM 47 / 48th

To 19 clock on June 28, 1941 sighted a lookout on the Tartar Lauenburg about 300 nautical miles north-east of Jan Mayen in the German naval grid square AB 72 As soon as the Tartar had come to artillery range, they opened fire. The crew of Lauenburg immediately went in two lifeboats. The Tartar came alongside and sent a prize crew on board, captured a large amount of papers. Then the Lauenburg was sunk. Among the captured documents were the new instructions for the plug connections and the attitude of the Enigma machine. This made it possible to decipher the radio messages of the Navy during much of the month of July 1941.