Jeremy Bernstein, writing in the New York Times, offers a concise history of how uranium centrifuges and other nuclear weapons technologies proliferated since the end of of the Second World War. As he says at the end of his piece, if someone had written the real story as a novel, nobody would have believed it.
A third group, headed by a physicist named Max Steenbeck, investigated the centrifuge. Dr. Steenbeck, who had been arrested by the Soviets and put in a concentration camp in Poland, had previously been in charge of research for the division of Siemens that dealt with aircraft. While in captivity he wrote a letter to the Soviet secret police, the N.K.V.D., explaining his scientific background; he also ended up in Sukhumi. Dr. Steenbeck began with a small group and some antiquated Soviet centrifuges that certainly could not have been used to separate uranium isotopes.
In the summer of 1946 they were joined by an Austrian physicist named Gernot Zippe. Dr. Zippe had been in the Luftwaffe during the war and, after having been taken prisoner in the summer of 1946, he went from a prison camp to the relative luxury of Sukhumi, thanks to the initiative of Dr. von Ardenne. Neither Dr. Zippe nor Dr. Steenbeck had ever worked on centrifuges, but within two years they created the best centrifuge in the world — although at the time they did not know it. (To give some idea of its capacity, a typical laboratory centrifuge makes a few thousand rotations a minute. The Zippe centrifuge — this is the common name, although Dr. Zippe himself refers to it as the “Russian centrifuge” — can do 90,000 rotations a minute.)
Read the whole thing. It is impossible to know exactly how much, if any, involvement the Pakistani government itself had in the spread of the technologies. But certain official factions may well have been involved. We can't find out because Pakistan will not allow Abdul Qadeer Khan to be interviewed. But both North Korea and Iran got their centrifuge technology from Pakistan at Khan's nuclear flea market.