Soviet biological weapons program that employed over 60,000 people for over twenty years. Since offensive biological weapons production was banned by treaty Biopreparat was kept secret by the military even from the highest levels of government, including the Soviet Premier. The sheer size of the operation required the creation of gigantic secret facilities. One of these facilities was hidden inside a city, Sverdlovsk, and was the tragic site of the largest biological weapons accident in history. Anthrax killed at least 68 people in Sverdlovsk and triggered a massive Soviet coverup. Curiously this occurred while Boris Yeltsin was First Secretary of the region. It was only after Ken Alibek, the Deputy Director of Biopreparat, defected to the US in 1992 that the full extent of the massive program was revealed to the West.