In the trail of an Enigma message |

Introduction |

The whole process of of encoding and decoding message is rather complex and can be very time consuming. Nevertheless, many Enigmae were used in the field and in U-boats. Setting up an Enigma and operating it, wasn't easy either. But the most difficult task that had to be carried out every day, was probably the breaking of the daily keys at Bletchley Park. This pages describes the path of a message, from the German Enigma operator in the field, to the Intelligence officers in the UK and elsewhere.

Sending a message |

Most confidential Army traffic on mainland Europe went over ordinary telephone lines. Radio links were used for those units that could not be contacted over land lines. Enigma messages were sent from the German High Command in Berlin to the various parts of the Army, all over the world. The units in the field could, of course, also report back to Berlin or to each other. Whenver a German commander wanted to send a message, he had to write it on paper and pass it on to the cypher clerk. The cypher clerk would then type the message on the Enigma (or pass it onto the Enigma operator) and write down the encode version of the message. The encoded message was then passed on to the radio operator, who would send the message in morse code. The image on the right, shows General Guderian standing in his command vehicle. The Enigma is in the bottom left of the picture. Behind it is the radio. As you can see, three operators were needed in the field to quickly send out an encoded message. |  |

Interception by the Y-Stations |

In order to copy with the large number of messages sent by the Germans each day, a big intercept organisation had to be exploited. This organisation would be called the Y Service. Hundreds of man and woman would write down long sequences of seemingly unrelated letters each day. |  |

The Teleprinter Room |

The Y Stations were scattered all over the UK, but were mainly located at the coast line, in order to avoid radio interference. Some German signals were so weak that the intercepts from several stations had to be combined in order to get a complete message. In the early days, messages were brought to Bletchley Park by courier, but later on in the war, teleprinters were used to send the messages via secure telephone lines. This photograph shows an example of a teleprinter room (not at BP). |  |

Breaking the Code |

Most of the messages were sent to Bletchley Park via teleprinter. Here is an example of a typical message at it was received by the BP cryptanalists. The codebreakers used coloured pencils to put their own markings on the paper sheet, as can be seen here. The letters MAFPKR were probably the initial settings for that day. Other markings show Red, to indicate the origin of the message (e.g. Luftwaffe) and 'Key 31/10' which tells us that the message was encrypted with the key for 31 October 1944. The message was received at Bletchley Park on 1 November 1944 as we can see in the preample of the message. |  |

The bombes |

Breaking the Enigma messages wasn't an easy job at all. Once the cryptanalists had a sufficiently large crib to work on they would use it to program the Bombe, which was some kind of mechanical computer. A crib is a part of the plaintext, that is likely to occur at the start of the message, 'to the chief in command'. The longer the crib, the easier it would be to break the key. The bombe shown here was used to break 3-wheel Enigma traffic. The machines used to break the 4-wheel Enigma messages, was even more complicated and had several extensions. |  |

Interpreting the message |

Once the key was broken, a modified British Type-X machine (the British variant of the Enigma) was used to decode the message. The Type-X machine would print it on long strokes of paper, which were glued to the back of the message. The message then went on to another part of Bletchley Park, were someone, capable of interpreting German, would clean up the message. Word breaks were added and typos were corrected. Once complete, the message was sent to the Intelligence department, who would use the contents of the message for strategic purposes. |  |

A real example of a message |

Below is an example of a real message as it was sent on 21 September 1938. The message was sent in three parts and is reproduced here with kind permission from Frode Weierud, Enigma Researcher.

`+ HRKM 13617 1807 - AN HEERESGRUPPENKOMMANDO 2= 06 18 24 (FRX) 2109 -1750 - 3 TLE - FRX FRX - 1TL -172= HCALN UQKRQ AXPWT WUQTZ KFXZO MJFOY RHYZW VBXYS IWMMV WBLEB DMWUW BTVHM RFLKS DCCEX IYPAH RMPZI OVBBR VLNHZ UPOSY EIPWJ TUGYO SLAOX RHKVC HQOSV DTRBP DJEUK SBBXH TYGVH GFICA CVGUV OQFAQ WBKXZ JSQJF ZPEVJ RO - 2TL - 166 - ZZWTV SYBDO YDTEC DMVWQ KWJPZ OCZJW XOFWP XWGAR KLRLX TOFCD SZHEV INQWI NRMBS QPTCK LKCQR MTYVG UQODM EIEUT VSQFI MWORP RPLHG XKMCM PASOM YRORP CVICA HUEAF BZNVR VZWXX MTWOE GIEBS ZZQIU JAPGN FJXDK I - 3TL - 176 - DHHAO FWQQM EIHBF BMHTT YFBHK YYXJK IXKDF RTSHB HLUEJ MFLAC ZRJDL CJZVK HFBYL GFSEW NRSGS KHLFW JKLLZ TFMWD QDQQV JUTJS VPRDE MUVPM BPBXX USOPG IVHFC ISGPY IYKST VQUIO CAVCW AKEQQ EFRVM XSLQC FPFTF SPIIU ENLUW O = 1 ABT GEN ST D H NR. 2050/38 G KDOS +`

Once it was decoded, it would look like this:

`AUF BEFEHL DES OBERSTEN BEFEHLSHABERS SIND IM FALLE X Z X ZT X UNWAHRSCHEINLICHEN X FRANZOESISQEN ANGRIFFS DIE WESTBEFESTIGUNGEN JEDER ZAHLENMAESSIGEN UEBERLEGENHEIT ZUM TROTZ ZU HALTEN X FUEHRUNG UND TRUPPE MUESSEN VON DIESER EHRENPFLIQT DURQDRUNGEN SEIN X ABS X DEM GEMAESS BEHALTE IQ MIR DIE ERMAEQTIGUNG ZUR PUFGABE DER BEFESTIGUNGEN ODER AUQ VON TEILEN AUSDRUECKLIQ PERSOENLIQ VOR X ABS X AENDERUNG DER ANWEISUNG X OKH X GEN X ST X D X H X ERSTE ABT X NR X DREI DREI ZWO EINS X DREI AQT G X KDOS X VOM JULI EINS NEUN DREI AQT BLEIBT VORBEHALTEN X DER OBERBEFEHLSHABER DES HEERES`

As the Enigma only contains the letters A-Z, a space and full-stop are missing. Furthermore, any special German characters, such as the ü (u-umlaut), had to be spelled in an alternative manner (e.g. 'ue'). Numbers were also missing on the Enigma keyboard and had to be spelled. In plain German, the message looks like this:

`Auf Befehl des Obersten Befehlshabers sind im Falle, (z.Zt =) zur Zeit unwahrscheinlichen, Franzoesischen Angriffs die Westbefestigungen jeder zahlenmaessigen Ueberlegenheit zum trotz zu halten. Fuehrung und Truppe muessen von dieser Ehrenpflicht durchdrungen sein. Dem gemaess behalte ich mir die Ermaechtigung zur Aufgabe der Befestigungen oder auch von Teilen ausdruecklich persoenlich vor. Aenderungen der Anweisung OKH/Gen/St/D/H Erste Abt Nr. 3321/38 G/KDos vom Juli 1938 bleibt vorbehalten. Der Oberbefehlshaber des Heeres.`

Translated into plain English, the message looks like this:

`The Commander-in-Chief orders as follows: In the case of French attacks on the western fortifications, although unlikely at this moment, those fortifications must be held at all costs, even against numerically superior forces. Commanders and troops must be imbued with the honour of this duty. In accordance with orders, I emphasise that I alone have the right to authorise the fortifications to be abandoned in whole or part. I reserve the right to make changes to the order OKH/Gen/St/D/H 1. Abt. Nr. 3321/38 GKDos of July 1938. The Commander-in-Chief of the Army.`

© Copyright Paul Reuvers. Last changed: Wed,15 Oct 2003.17:28:04