It was in the Kabaty Woods, at Pyry, on 25 and 26 July 1939, with war looming, that, on instructions from the Polish General Staff, the Cipher Bureau's chiefs, Lt. Col. Gwido Langer and Major Maksymilian Ciężki, the three civilian mathematician-cryptologists, and Col. Stefan Mayer, chief of intelligence, revealed Poland's achievements to cryptanalytical representatives of France and Britain, explaining how they had broken Enigma. They undertook to give each country a Polish-reconstructed Enigma, along with details of their equipment, including Zygalski sheets and Rejewski's cryptologic bomb. In return, the British pledged to prepare two full sets of Zygalski sheets for all 60 possible wheel orders. The French contingent consisted of Major Gustave Bertrand, the French radio-intelligence and cryptology chief, and Capt. Henri Braquenié of the French Air Force staff. The British sent Commander Alastair Denniston, head of Britain's Government Code and Cypher School, Dilly Knox, chief British cryptanalyst and Commander Humphrey Sandwith, head of the Royal Navy's intercept and direction-finding stations.