On August 21, 1968, Russian tanks rolled into Czechoslovakia (known officially as the Czechoslovak Socialist Republic) to protect Soviet interests in what had been a Communist state within the Eastern Bloc since the Second World War (or more precisely, a Communist coup d’état in February 1948).
Life in Czechoslovakia was extremely repressive during the 1950s and early 1960s, but the regime became more open and tolerant under Alexander Dubček (see Bookmark, page 26) during the “Prague Spring” of 1968. The Soviets invaded openly and forcefully to reimpose the conditions of the post-World War II Warsaw Treaty, and NATO and the U.S. did not respond as harsh conditions returned in the late 1960s and 1970s. The country would not be free of Soviet control until the “Velvet Revolution” of 1989-1991 (and the collapse of the Soviet Union) broke the hold of the Warsaw Treaty over Eastern Europe and what became the Czech Republic.
The larger political developments of 1968 are an integral part of the plot of The Unbearable Lightness of Being: they affect the fortunes of all the principal characters (from Tereza’s joyful photography during the invasion to Tomas’s dismissal from the hospital) and the choices they make (especially their various forms of escape -- Tomas and Tereza to the country, Sabina to Geneva, then Paris and the U.S.).