<human>:  How did the Soviet Union respond to the demonstrations in Prague in 1968?
<bot>: The Soviet Union responded to the demonstrations in Prague in 1968 by sending in troops to suppress the protests and take control of Czechoslovakia. This action, known as the Warsaw Pact invasion, was a move seen by many as a direct violation of Czechoslovakia's sovereignty and an indication of the Soviet Union's willingness to use force to maintain communist rule in Europe.