The Pyry Forest Handover

1939 · Enigma Doubles · Work 445 of 1,871

The Pyry Forest Handover, 1939, Enigma Doubles

A low concrete room of an underground cipher-bureau bunker, bare concrete walls and a vaulted ceiling, a single caged electric bulb hanging from the ceiling, two wooden crates standing open on the concrete floor, an Enigma replica packed in wood wool inside one of them, papers and wiring diagrams stacked in the other, a plain wooden table with a second machine under a cloth, a steel door standing ajar onto a dark corridor.

What it was used for
A meeting at the Polish Cipher Bureau's radio intelligence centre at Pyry outside Warsaw. The Polish side disclosed to its British and French guests what it had known since 1932 about the steckered army Enigma, and handed over reconstructed machines. A letter from Tadeusz Lisicki reproduced by Joel Greenberg dates the meeting to 25 and 26 July 1939 and names Alastair Denniston and Dillwyn Knox for the British side; the science portal of the Polish Press Agency PAP gives 25 July 1939. According to Lisicki, citing Colonel Mayer, "the two Enigma machines were send by diplomatic bag by sea from Gdynia to France and one was later delivered by Bertrand to London".
What was new
What was handed over was not just a device but an approach: that Enigma yields to permutation mathematics rather than to a feel for language. Marek Grajek, author of "Enigma. Bliżej prawdy", records that the break had been considered impossible and that the Polish success rested on mathematical rather than linguistic methods. Even the list of attendees has come down with errors: Lisicki's letter on Greenberg's page lists "Menzies incognito" for the British side, and Greenberg corrects this in a footnote to Sandwith. The barb is the date. Five weeks separated the handover from the German attack on Poland; the Poles gave away everything they had and afterwards carried on in exile, first in France.

Connections

Every connection names its kind. “Forerunner” on its own would be a claim.

  1. EncounteredThe Bomba Kryptologiczna1938On 25 and 26 July 1939 Polish, French and British cryptanalysts met outside Warsaw, at the Polish decryption centre at Pyry; Alastair Denniston and Dilly Knox came for Britain. There the visitors learned of the design and construction of the bomba kryptologiczna, which GCHQ calls the first electromechanical device used to support cryptanalysis.Source: GCHQ: The Pyry Forest Meeting · Agencja Wywiadu (Polen): Enigma decryption · Gordon Welchman, From Polish Bomba to British Bombe: The Birth of Ultra, Intelligence and National Security 1:1 (1986), S. 71-110
  2. Follows fromEnigma I with Plugboard1932At Pyry in the Kabacki Forest near Warsaw, on 25 and 26 July 1939, the Poles handed over two reverse-engineered copies of the German machine, one each for France and Britain, together with their methods. These Enigma doubles came out of the Polish reconstruction of the plugboard military machine.Source: Elizabeth Bruton u. a.: Zygalski sheets - Polish codebreaking and the role of reconstruction in the Top Secret exhibition at the Science Museum. Science Museum Group Journal (Ort, Enigma Double) · Jennifer Wilcox: Solving the Enigma - History of the Cryptanalytic Bombe. Center for Cryptologic History, National Security Agency (Datum 25./26. Juli 1939)

Further reading