Admiralty: Department of the British government responsible for command of the Royal Navy.
Asdic: A device that uses reflected sound waves to detect objects underwater. Named for the Allied Submarine Detection Investigation Committee that developed it. Often called sonar, especially in American English.
Befehlshaber der Unterseeboote (BdU): Headquarters of the supreme command of the Kriegsmarine’s U-boat arm.
Bigram Table: These sheets were used to encipher the starting positions of the rotors for an Enigma message. The indicators were then transmitted with the message so the receiver could use his own copy of the table to find the correct settings with which to decipher the message. The tables were updated frequently.
Bold: A German sonar decoy canister used by U-boats to confuse ships attempting to hunt them. When the calcium hydride inside mixed with ocean water, it created a mass of bubbles.
Bombe: A machine used to test various Enigma settings in order to narrow down the possibilities. Development was headed by Alan Turing and refined by Gordon Welchman, with inspiration from a similar machine (the bomba) built by Polish cryptographers.
Bletchley Park: British codebreaking center in Buckinghamshire, England.
Cipher: Ciphers and codes are ways of obscuring a message from anyone who does not have the key. The terms are often used interchangeably, but in a strict sense, codes substitute something else in place of the original message. Morse code, for example, replaces letters with dots and dashes. Ciphers use a formula, algorithm, or machine to transform the original message into a seemingly random string of letters.
Crib: An educated guess of what an enciphered message says, used in an attempt to decipher the message. For example, if a German minesweeper cleared a minefield, that report might be sent to a U-boat in the Shark Enigma cipher and also to a tugboat in the less complicated Dockyard cipher. If the message sent in Dockyard were broken, it could become a crib for the Shark message. Once codebreakers knew what the Shark message said, they could determine the day’s Enigma settings.
Devil’s Shovel: Slang term for a U-boat.
Enigma: Machine used to encrypt and decrypt German military messages before and during WWII. The Enigma was portable and fairly easy to operate. When one letter was pressed on a typewriter-like keyboard, another letter lit up on the machine’s lamp board, and the letters from the lamp board were recorded as the encryption. As long as the same settings were used, the process also worked in reverse so the receiver could decrypt and read the message. Different settings were created by using different combinations of rotors that had the alphabet printed along the outside edge. Machines used three rotors at a time (four later in the war for the Naval Enigma), and an astronomically high number of settings were possible based on which rotors were used, in which order, with which ring settings (how the rotors were connected internally), and with which starting point. The machine also included an external plug board that further scrambled the letters.
Funkgast: Radio operator on a U-boat.
Funkmaat: Radio petty officer on a U-boat.
Heer: German Army.
Kapitänleutnant: Officer in the German Kriegsmarine, rank similar to a lieutenant commander in the Royal Navy or U.S. Navy.
Kommandant: Commanding officer of a ship.
Kriegsmarine: German Navy.
Luftwaffe: German Air Force.
Meteorologe: Meteorologist in the Kriegsmarine.
Metox: A radar detection device used on U-boats to alert them of enemy aircraft using radar even before the aircraft was visible.
Oberfunkmeister: Senior radio petty officer on a U-boat.
Oberleutnant zur See: Officer in the German Kriegsmarine, rank similar to a sublieutenant in the Royal Navy or a lieutenant (junior grade) in the U.S. Navy.
Shark: The Naval Enigma network used by U-boats after October 1941. Shark is the British name for it. The Kriegsmarine called it Triton.
SSS: Maritime distress signal indicating a ship has been attacked by a submarine. During later periods of the war, SSSS was used instead.