Political map of Russia & the former Soviet Union 26 June 1963 (Height of the Cold War): Although the Warsaw Pact (Warsaw Pact) was officially a defensive alliance, attempts to break with the Pact were crushed in Hungary (1956) (Hungarian Revolution of 1956) and Czechoslovakia (1968) (Warsaw Pact invasion of Czechoslovakia). Confrontation with the United States (Cold War) peaked in the early 1960s with the Arms Race (nuclear arms race), the construction of the Berlin Wall (1961) (Berlin Crisis of 1961), the Cuban Missile Crisis (1962) (Cuban Missile Crisis), and the Vietnam War (Vietnam War).