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 [by the Germans]." Polish Navy The first Polish military branch to transfer substantial personnel and equipment to the United Kingdom was the Polish Navy. Shortly before the outbreak of hostilities, the Polish government ordered three destroyers, for their protection and in anticipation of joint operations with the Royal Navy, to sail for Great Britain (Operation Peking). Two submarines also sailed there, the Orzeł (Eagle) arriving unannounced in Scotland after a daring breakout from the Baltic Sea following its illegal internment in Estonia. Polish Navy personnel to come under Royal Navy command comprised 1,400 officers and 4,750 sailors. By chance, Poland's only two ocean-going commercial liners, MS Piłsudski and MS Batory were also on the high seas on 1 September 1939 and were both shortly thereafter requisitioned by the British Admiralty for war service. The former was lost in November 1939 when it struck a mine off the Yorkshire coast. Batory, dubbed "the Lucky ship", became a troop and civilian carrier and hospital ship. It effected a major evacuation during the Battle of Narvik and completed hundreds of convoys on the Mediterranean Sea and on the Atlantic, before being surrendered to the control of the communist authorities in Warsaw in 1946. In May 1941, the Polish destroyer Piorun—Thunderbolt—was able to locate and engage the world's most powerful battleship,