Soon after the invasion of Poland by Germany on 1 September 1939, key Cipher Bureau personnel were evacuated southeastward; on 17 September, as the Soviet Union attacked Poland from the East, they crossed into Romania. From there they reached Paris, France; at PC Bruno, near Paris, they continued working toward breaking Enigma, collaborating with British cryptologists at Bletchley Park as the British got up to speed on their work breaking Enigma. In due course, the British cryptographerswhose ranks included many chess masters and mathematics dons such as Gordon Welchman, Max Newman, and Alan Turing (the conceptual founder of modern computing) made substantial breakthroughs in the scale and technology of Enigma decryption.