Bulgaria–United States relations to work. Bulgaria became a member of the Warsaw Pact on May 14, 1955. Though no Soviet troops were stationed on Bulgarian soil, in 1968, Zhivkov sent a Bulgarian division to join Polish, Hungarian and Soviet troops to crush a popular uprising in Prague. In 1978, the Bulgarian secret police were implicated in the assassination in London of Georgi Markov, a Bulgarian dissident who was a correspondent for the BBC World Service, Deutsche Welle radio and the U.S. sponsored Radio Free Europe. Markov was assassinated with a poisoned umbrella on September 7, Zhivkov's birthday. The rise of democratic movements across
Assassination assassinated by ricin poisoning. A tiny pellet containing the poison was injected into his leg through a specially designed umbrella. Widespread allegations involving the Bulgarian government and KGB have not led to any legal results. However, after the fall of the USSR, it was learned that the KGB had developed an umbrella that could inject ricin pellets into a victim, and two former KGB agents who defected said the agency assisted in the murder. The CIA made several attempts to assassinate Fidel Castro, many of the schemes involving poisoning his cigars. In the late 1950s, KGB assassin Bohdan Stashynsky killed