The Czechoslovak crisis, as it came to be known, started in January 1968, when Alexander Dubcek was elevated to the post of First Secretary of the Communist Party of Czechoslovakia (CPCz), replacing moribund Antonin Novotny, who had served as First Secretary since 1957. Under Dubcek, the communist leadership embarked on a program of dramatic liberalization of the Czechoslovak political, economic, and social order, including the overhaul of the CPCz leadership, increased freedom of speech, surrender of authority to the Czech National Assembly by the Communist Part, real elections as local and national levels, and even the suggestion of legalizing non-communist political parties. In all, the crisis lasted more than a year, with the first none months consisting of Czech reforms triggering Soviet statements of concern and eventually threats, buttressed by Warsaw Pact military buildups disguised as exercises. When the invasion occurred in the early morning hours of 21 August, the Czechoslovak leadership as not immediately removed, but remained largely intact through April 1969, when Dubcek was finally replaced as First Secretary by a more pro-Soviet Gustav Husak. All this alarmed Moscow and the leadership of the Warsaw Pact, but throughout the Prague Spring, Dubcek went out of his way to demonstrate his personal loyalty to Moscow and Prague's intention to remain firmly within the Warsaw Pact military alliance. How sincere he was in these remonstrations is difficult to say, but Dubcek and his allies clearly feared a repetition of the Hungarian uprising of 1956, brutally crushed by Soviet troops. These fears were mirrored in Washington and, to a certain extent, even in Moscow.