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
1978 Balkan Bulgarian Tupolev Tu-134 crash 1978 Balkan Bulgarian Tupolev Tu-134 crash The 1978 Balkan Bulgarian Tupolev Tu-134 crash was an accident that occurred on 16 March 1978, when a Balkan Bulgarian Airlines Tupolev Tu-134 airliner on an international flight from Sofia, Bulgaria, to Warsaw Airport, Poland crashed. On departure from Sofia, the aircraft was climbing to , but at it turned on a heading of 050. It turned again to 270 then began an abnormal descent. The aircraft crashed near the village of Gabare, 130 km northeast of Sofia. All 73 on board died. It was never established what the nature of the emergency was