In the other satellites Soviet domination increased until 1955: in 1952, 80 per cent of Soviet trade was with the satellites. In 1954 the USSR granted a degree of economic independence to East Germany, which was freed from further reparations payments but retained a large contingent of Soviet troops. Formation of the Warsaw Pact for military assistance in 1955 was a countermeasure to NATO and served to tighten Soviet control. After the death of Stalin, relations with Yugoslavia improved, only to decline again, especially after the invasion of Czechoslovakia in 1968. After 1961 the Soviet Union completely lost control of Albania, which until 1978 remained closely allied with China.

Polish and Hungarian Crises

Soviet control of the satellites was most seriously threatened in 1956, during the relaxation following de-Stalinization. Popular discontent and demonstrations in Poland in 1956 were followed by an enforced change of government in Poland and a "temporary" continuance of Soviet troops in Poland, cancellation of some Polish debts, and the granting of additional credits.

The Hungarian uprising later in the year was more serious. Demonstrations by workers and students for national independence led to the intervention of Soviet troops, which brutally subdued the independence movement, killing thousands and imprisoning many more, and the formation of a new puppet government under János Kádár. The USSR was condemned by the Western countries and by the United Nations, but for a long time afterwards it maintained a great degree of control in Hungary.

Prague Spring

The next crisis, in Czechoslovakia in the summer of 1968, reflected the more relaxed Soviet system of review after 1960 and the pressure for economic change within the Czechoslovak Communist party, which was dismayed by the stagnant economy and sought to create "socialism with a human face". Dissatisfaction and clamour for reform led peacefully and gradually to the replacement of Antonín Novotnýas head of the party and of the state by Alexander Dubcek and Ludvík Svoboda, both Communists long loyal to the Soviet Union. Soviet leaders were alarmed by the "Prague Spring"-particularly by the ending of censorship and talk of closer economic relations with the West. Pressure was brought to bear in various ways, but when all other means failed, approximately 600,000 Soviet and other Warsaw Pact (except Romanian) troops were airlifted into Prague and occupied Czechoslovakia on the night of August 20, 1968. Passive resistance was united and most impressive, but the Soviet forces gradually won the day.