''Lauenburg'' was a German weather ship used in the early years of the

Second World War World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposi ...

to provide weather reports for German shipping, particularly German

U-boats U-boats were naval submarines operated by Germany, particularly in the First and Second World Wars. Although at times they were efficient fleet weapons against enemy naval warships, they were most effectively used in an economic warfare rol ...

. After the German use of such vessels had been identified as a weakness that could be exploited to break the Enigma code, ''Lauenburg'' was captured and sunk on 28 June 1941. The

Royal Navy The Royal Navy (RN) is the United Kingdom's naval warfare force. Although warships were used by English and Scottish kings from the early medieval period, the first major maritime engagements were fought in the Hundred Years' War against ...

acquired important German code books and parts of an Enigma machine.

Early life

''Lauenburg'' had been built in 1938 as a

fishing trawler A fishing trawler is a commercial fishing vessel designed to operate fishing trawls. Trawling is a method of fishing that involves actively dragging or pulling a trawl through the water behind one or more trawlers. Trawls are fishing nets th ...

, named after the town of

Lauenburg Lauenburg (), or Lauenburg an der Elbe ( en, Lauenberg on the Elbe), is a town in the state of Schleswig-Holstein, Germany. It is situated on the northern bank of the river Elbe, east of Hamburg. It is the southernmost town of Schleswig-Holstein ...

, and with the identification number 'PG 532'. She operated out of Geestemünde for her owners, H. Bischoff & Co, of Bremen. She was acquired by the '' Kriegsmarine'' in 1940, and entered naval service in November, having been converted into a weather ship, retaining the name ''Lauenburg''. In her new guise she carried a crew of between 19 and 21, as well as eight

meteorologists A meteorologist is a scientist who studies and works in the field of meteorology aiming to understand or predict Earth's atmospheric phenomena including the weather. Those who study meteorological phenomena are meteorologists in research, while t ...

. She was to be used to provide detailed weather reports for naval units, including Germany's

U-boat U-boats were naval submarines operated by Germany, particularly in the First and Second World Wars. Although at times they were efficient fleet weapons against enemy naval warships, they were most effectively used in an economic warfare ro ...

fleet.

The weather ships and Enigma

The

British British may refer to: Peoples, culture, and language * British people, nationals or natives of the United Kingdom, British Overseas Territories, and Crown Dependencies. ** Britishness, the British identity and common culture * British English, ...

cryptologist This is a list of cryptographers. Cryptography is the practice and study of techniques for secure communication in the presence of third parties called adversaries. Pre twentieth century * Al-Khalil ibn Ahmad al-Farahidi: wrote a (now lost) bo ...

Harry Hinsley Sir Francis Harry Hinsley, (26 November 1918 – 16 February 1998) was an English historian and cryptanalyst. He worked at Bletchley Park during the Second World War and wrote widely on the history of international relations and British Int ...

, then working at

Bletchley Park Bletchley Park is an English country house and estate in Bletchley, Milton Keynes ( Buckinghamshire) that became the principal centre of Allied code-breaking during the Second World War. The mansion was constructed during the years followin ...

, realised at the end of April 1941 that the German weather ships, usually isolated and unprotected trawlers, were using the same

Enigma Enigma may refer to: *Riddle, someone or something that is mysterious or puzzling Biology *ENIGMA, a class of gene in the LIM domain Computing and technology * Enigma (company), a New York-based data-technology startup * Enigma machine, a family ...

code books as were being used on U-boats. The trawlers, which transmitted weather reports to the Germans, were being sent naval Enigma messages. Although the weather ships did not transmit enciphered weather reports on Enigma machines, they needed one to decode the Enigma signals transmitted to them. Hinsley realised that if the code books could be captured from one of these trawlers, the naval Enigma system could be broken, with British intelligence able to decipher messages to U-boats and discover their locations. The problem remained that if the navy were to attempt to capture one of the weatherships, the German crew would have time to throw their Enigma settings into the sea before they were boarded. Hinsley instead reasoned that the following month's Enigma settings would be locked in a safe aboard the ship and could be overlooked if the Germans were surprised and forced hastily to abandon ship. The

Admiralty Admiralty most often refers to: *Admiralty, Hong Kong *Admiralty (United Kingdom), military department in command of the Royal Navy from 1707 to 1964 *The rank of admiral *Admiralty law Admiralty can also refer to: Buildings * Admiralty, Traf ...

despatched seven destroyers and cruisers to the northeast of

Iceland Iceland ( is, Ísland; ) is a Nordic island country in the North Atlantic Ocean and in the Arctic Ocean. Iceland is the most sparsely populated country in Europe. Iceland's capital and largest city is Reykjavík, which (along with its s ...

at the beginning of May 1941. The target was ''München'', one of the weather ships operating in the area. The weather ship and the Enigma settings for June 1941 were captured and naval Enigma messages transmitted during June 1941 were quickly deciphered. Halfway through June 1941 the Germans replaced the

bigram A bigram or digram is a sequence of two adjacent elements from a string of tokens, which are typically letters, syllables, or words. A bigram is an ''n''-gram for ''n''=2. The frequency distribution of every bigram in a string is commonly used f ...

tables used in Enigma. This would have resulted in a codebreaking blackout unless further settings could be captured. Hinsley and the Admiralty were concerned that capturing another weather ship might alert the Germans to their vulnerability and cause them to immediately alter them. It was eventually decided to take the risk and on 25 June 1941, the

light cruiser A light cruiser is a type of small or medium-sized warship. The term is a shortening of the phrase "light armored cruiser", describing a small ship that carried armor in the same way as an armored cruiser: a protective belt and deck. Prior to th ...

and the

destroyers In naval terminology, a destroyer is a fast, manoeuvrable, long-endurance warship intended to escort larger vessels in a fleet, convoy or battle group and defend them against powerful short range attackers. They were originally developed in ...

, and , were despatched from Scapa Flow to capture the codebooks from ''Lauenburg'', another weather ship operating north of Iceland, which Hinsley had selected.

Capture and sinking of ''Lauenburg''

At around 7pm on 28 June, a lookout aboard ''Tartar'' sighted ''Lauenburg'' off

Jan Mayen Jan Mayen () is a Norwegian volcanic island in the Arctic Ocean with no permanent population. It is long (southwest-northeast) and in area, partly covered by glaciers (an area of around the Beerenberg volcano). It has two parts: larger ...

and the destroyer opened fire. ''Lauenburg's'' crew quickly abandoned the ship in two lifeboats. Minutes later, ''Tartar'' steamed alongside and a boarding party seized ''Lauenburg'' and a large amount of material was collected, then the Allied warships sank ''Lauenburg'' with gunfire; confirmation of the sinking was sent by radio, but the boarding was specifically not mentioned so that listening Germans would not suspect the recovery of Enigma materials.Dr. Mark Baldwin, "The Enigma Machine", presentation to the BCS Tayside & Fife Branch, Abertay University, 26 August 2019 The recovered material allowed further understanding of the Enigma codes and resulted in faster decoding of encrypted messages, as well as providing an up-to-date set of codes.

References

Breaking the Enigma code

Breaking Germany's Enigma Code

{{DEFAULTSORT:Lauenburg Auxiliary ships of the Kriegsmarine Ships built in Kiel Enigma machine 1938 ships Trawlers Maritime incidents in June 1941 World War II shipwrecks in the Arctic Ocean Weather ships

Early life

The weather ships and Enigma

Capture and sinking of ''Lauenburg''

See also

References