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
2003 ricin letters 2003 ricin letters The 2003 ricin letters refer to two ricin-laden letters found on two separate occasions between October and November 2003. One letter was mailed to the White House and intercepted at a processing facility; another was discovered with no address in South Carolina. A February 2004 ricin incident at the Dirksen Senate Office Building was initially connected to the 2003 letters as well. The letters were sent by an individual calling him- or herself "Fallen Angel". The sender, who claimed to own a trucking company, expressed anger over changes in federal trucking regulations. As of 2008, no connection