The Short Signal Code, also known as the Short Signal Book (), was a short code system used by the

Kriegsmarine The (, ) was the navy of Nazi Germany from 1935 to 1945. It superseded the Imperial German Navy of the German Empire (1871–1918) and the inter-war (1919–1935) of the Weimar Republic. The was one of three official military branch, branche ...

(German Navy) during

World War II World War II or the Second World War (1 September 1939 – 2 September 1945) was a World war, global conflict between two coalitions: the Allies of World War II, Allies and the Axis powers. World War II by country, Nearly all of the wo ...

to minimize the transmission duration of messages.

Description

The transmission of radio messages had the potential risks of revealing the submarine's presence and direction; if decoded the content was also revealed. Submarines need to provide information, mostly in standard form (position of convoy to attack and of submarine, weather information), to their bases. Initially Morse code transmissions could be used. To inhibit detection, the duration of messages needed to be minimised; for this, ''Kurzsignale'' short-coding was used. To prevent interception, messages needed to be encrypted by the

Enigma machine The Enigma machine is a cipher device developed and used in the early- to mid-20th century to protect commercial, diplomatic, and military communication. It was employed extensively by Nazi Germany during World War II, in all branches of the W ...

. To shorten transmission even further, the message could be sent by a fast machine instead of a human radio operator. For example, the Kurier system – not implemented in time – decreased the time to send a Morse dot from around 50 milliseconds for a human to 1 millisecond.

Short Signal book

The ''Kurzsignale'' code was intended to shorten transmission time to below the time required to get a directional fix. It was not primarily intended to hide signal contents; protection was intended to be achieved by encoding with the Enigma machine. A copy of the ''Kurzsignale'' code book was captured from on 9 May 1941. In August 1941, Dönitz began addressing U-boats by the names of their commanders, instead of boat numbers. The method of defining U-boat meeting points in the Short Signal Book was regarded as compromised, so a method was defined by

B-Dienst The ''B-Dienst'' (, observation service), also called x''B-Dienst'', X-''B-Dienst'' and χ''B-Dienst'', was a Department of the German Naval Intelligence Service (, MND III) of the Oberkommando der Marine, OKM that dealt with the interception and ...

cryptanalysts to disguise their positions on the Kriegsmarine German Naval Grid System (German:Gradnetzmeldeverfahren) was introduced and used until the end of the war

Radio direction finding

Aware of the danger presented by

radio direction finding Direction finding (DF), radio direction finding (RDF), or radiogoniometry is the use of radio waves to determine the direction to a radio source. The source may be a cooperating radio transmitter or may be an inadvertent source, a natural ...

(RDF), the

developed various systems to speed up broadcast. The ''Kurzsignale'' code system condensed messages into short codes consisting of short sequences for common terms such as "convoy location" so that additional descriptions would not be needed in the message. The resulting ''Kurzsignal'' was then encoded with the Enigma machine and subsequently transmitted as rapidly as possible, typically taking about 20 seconds. Typical length of an information or weather signal was about 25 characters. Conventional RDF needed about a minute to fix the bearing of a radio signal, and the Kurzsignale protected against this. However, the

huff-duff High-frequency direction finding, usually known by its abbreviation HF/DF or nickname huff-duff, is a type of radio direction finder (RDF) introduced in World War II. High frequency (HF) refers to a radio band that can effectively communicate ove ...

system which was in use by the Allies could cope with these short transmissions. The fully automated

burst transmission Burst may refer to: *Burst mode (disambiguation), a mode of operation where events occur in rapid succession **Burst transmission, a term in telecommunications **Burst switching, a feature of some packet-switched networks **Bursting, a signaling mo ...

''Kurier system'', in testing from August 1944, could send a ''Kurzsignal'' in not more than 460 milliseconds; this was short enough to prevent location even by

and, if deployed, would have been a serious setback for Allied anti-submarine and code-breaking activities. By late 1944 the ''Kurier'' program was a top priority, but the war ended before the system was operational.Aircraft of World War II: thread August 19, 1942
/ref>

Short Weather cipher

A similar coding system was used for weather reports from U-boats, the '' Wetterkurzschlüssel'' (Short Weather Cipher). Code books were captured from on 30 October 1942.

References

{{reflist, 30em Kriegsmarine Cryptography History of telecommunications in Germany Signals intelligence of World War II Military communications of Germany Military history of Germany during World War II World War II military equipment of Germany