From Fire Signals to ADFGX: A Case Study in the Adaptation of Ancient Methods of Secret Communication

Martine Diepenbroek

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Very early-on in Greek history mountaintops were already used as watch-towers and signalling stations from which messages could be sent over long distances by fire signals. In these earliest examples it was only possible to send one prearranged message, something that was often not sufficient in case communicating parties needed to communicate on urgent matters. The fourthcentury BC military author Aeneas Tacticus accordingly invented a method for fire signalling, whereby a series of messages could be sent related to events that often occur in warfare. The system might have been used as a cryptographic device. Due to errors in Aeneas’ system, Polybius improved another system based on the same principles, which in turn formed the basis for the modern ‘Polybius square’, used by the Germans for their ADFGX- and ADFGVX-ciphers: secret cipher systems used in the First World War. There is no clear evidence linking Aeneas’ fire signalling method directly to the German ciphers. However, it will be shown that Polybius used Aeneas’ system in his own fire signalling method. Polybius’ method in turn impacted the development of the Polybius square and its use in the ADFGX and ADFGVX ciphers. By analysing the ancient history of Polybius’ method for fire signalling and the merits of applying this to the use of the square in the German ciphers, it will be shown how an ancient fire signalling method inspired modern ciphers.
Original languageEnglish
Pages (from-to)63-76
Number of pages14
JournalKLEOS - The Amsterdam Bulletin of Ancient Studies and Archaeology
Issue number2
Publication statusPublished - 29 Apr 2019


  • Cryptography
  • Fire signalling
  • Aeneas Tacticus
  • Polybius
  • First World War


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