One of the most important Polish contributions to Allied victory had actually begun in late 1932, nearly seven years before the outbreak of war when the mathematician-cryptologist Marian Rejewski, with limited aid from French military intelligence, constructed a double of the sight-unseen German Enigma cipher machine used by the German civil and military authorities. Five weeks before the outbreak of war, in late July 1939, Rejewski and his fellow cryptologists, Henryk Zygalski and Jerzy Rozycki had disclosed to French and British intelligence in Warsaw the techniques and technologies they had developed for "breaking" German Enigma ciphers. Poland's "Biuro Szyfrów" (Cipher Bureau, operated by the Polish General Staff) gave the British and French an Enigma double, each. This enabled the British, who had been unable to break German Enigma ciphers at Bletchley Park, to develop their "Ultra" operation. At war's end, General Dwight Eisenhower characterized Ultra as having been "decisive" to Allied victory. Former Bletchley Park cryptologist Gordon Welchman wrote: "Ultra would never have got off the ground if we had not learned from the Polish, in the nick of time, details both of the German military... the Enigma machine, and of the operating procedures that were in use the Germans."