Lauenburg (ship)
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 north German city of Lauenburg . The WBS had the task of delivering weather reports to the German naval command and in particular for the submarines leading to the trade war .
With the capture and subsequent sinking of the Lauenburg on June 28, 1941, the Royal Navy succeeded in obtaining important German code books and instructions for setting up the Enigma cipher machine .
Early career
The Lauenburg (identification number PG 532) was a trawler of the Bremen fishing company H. Bischoff & Co. which was laid on July 1, 1936 and completed in 1938 and operated from the home port of Geestemünde . In 1940 the ship was requisitioned by the Kriegsmarine and, after appropriate modifications, put into service in November 1940 as weather observation ship 3 (WBS 3). The crew now consisted of 19-21 men and eight meteorologists .
The weather observation ships and the Enigma
The British cryptanalyst Harry Hinsley , who worked at Bletchley Park , came to the conclusion in April 1941 that the German WBS, unarmed and lonely in their positions, were using the same Enigma machines and code books as the German submarines. Although encrypted the WBS not their weather reports with the Enigma, but they needed the codes to looking at her radio messages decipher . If one could steal such keyboards from one of these WBS, one would be able to break the Enigma radio traffic of the Kriegsmarine and thus read radio messages to and from U-boats and determine their positions. Although it was assumed that the crew of an attacked WBS would throw the currently valid Enigma settings and codebooks overboard, Hinsley believed that the settings for the following month would likely be locked in a safe and left there by the crew if they were would be forced to leave their ship quickly.
The British Admiralty was persuaded and in early May 1941 sent seven cruisers and destroyers to the sea area northeast of Iceland , where the destroyer HMS Somali captured the WBS Munich on May 7 and captured the Enigma key settings for the month of June. The navy radio messages were thus deciphered very quickly in June.
When the German naval command changed the bigram tables used for the Enigma , the so-called double - letter exchange tables, in mid-June , it became necessary for the Royal Navy to steal the new documents. Although they were aware of the risk that the capture of another WBS could point the German naval command to this weak point within such a short time, the light cruiser HMS Nigeria and the destroyers HMS Tartar , HMS Jupiter and HMS Bedouin were taken from on June 25, 1941 Scapa Flow set out on the march to conquer the WBS Lauenburg located in the lake area around Jan Mayen . On the march north, the commander of the Tartar instructed his artillery boatman that he should not hit the Lauenburg under any circumstances, but only get the crew to leave their ship as quickly as possible.
The capture of the Lauenburg
The Lauenburg left Trondheim on May 27, 1941, heading for their area of operations OG 3 north-east of Jan Mayen. On June 2, she began sending out her weather reports from marine grid square AB 47/48.
Around 7 p.m. on June 28, 1941, a lookout on the Tartar sighted the Lauenburg about 300 nautical miles northeast of Jan Mayen in the German naval plan square AB 72. As soon as the Tartar was within artillery range, it opened fire. The crew of the Lauenburg immediately went into two lifeboats. The Tartar went alongside and sent a prize squad on board, which 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 internal settings of the Enigma machine. This made it possible to decipher the radio messages of the Kriegsmarine during almost the entire month of July 1941.