When Alexander Dubcek replaced conservative, pro-Moscow leader Novotny in January 1968, he began to implement reform, including removing censorship of press, de-collectivisation, increased trade with West, freedom to travel. The ‘Prague Spring’ is known as the time when these reforms were implemented. Despite increasing interactions with the West, Dubcek wished to remain in the Warsaw Pact as a military ally of the Soviet Union. He wanted Czechoslovakia to remain communist but with some features of democracy- “socialism with a human face”
However, the Soviets viewed such reforms as a move towards capitalism, stating:
“We cannot agree to have hostile forces push your country away from the road of socialism. We cannot accept the risk of Czechoslovakia being cut off from the socialist community of countries.” 15th July 1968, letter of warning from Soviet leadership to the Czechoslovakian Communist Party