The post-1956 liberalizing trend, in decline for a number of years, was reversed in March 1968, when student demonstrations were suppressed during the 1968 Polish political crisis. Motivated in part by the Prague Spring movement, the Polish opposition leaders, intellectuals, academics and students used a historical-patriotic Dziady theater spectacle series in Warsaw as a springboard for protests, which soon spread to other centers of higher education and turned nationwide. The authorities responded with a major crackdown on opposition activity, including the firing of faculty and the dismissal of students at universities and other institutions of learning. At the center of the controversy was also the small number of Catholic deputies in the Sejm (the Znak Association members) who attempted to defend the students.

In an official speech, Gomułka drew attention to the role of Jewish activists in the events taking place. This provided ammunition to a nationalistic and antisemitic communist party faction headed by Mieczysław Moczar that was opposed to Gomułka's leadership. Using the context of the military victory of Israel in the Six-Day War of 1967, some in the Polish communist leadership waged an antisemitic campaign against the remnants of the Jewish community in Poland. The targets of this campaign were accused of disloyalty and active sympathy with Israeli aggression. Branded "Zionists", they were scapegoated and blamed for the unrest in March 1968, which eventually led to the emigration of much of Poland's remaining Jewish population (about 15,000 Polish citizens left the country).

With the active support of the Gomułka regime, the Polish People's Army took part in the infamous Warsaw Pact invasion of Czechoslovakia in August 1968, after the Brezhnev Doctrine was informally announced.