Using strikes and other protest actions, Solidarity sought to force a change in government policies. In some cases, as in Bielsko-Biała, Solidarity managed to force corrupt officials of the government to lose their jobs. At the same time, it was careful never to use force or violence, so as to avoid giving the government any excuse to bring security forces into play. After 27 Bydgoszcz Solidarity members, including Jan Rulewski, were beaten up on March 19, a four-hour warning strike on March 27, involving around twelve million people, paralyzed the country. This was the largest strike in the history of the Eastern bloc, and it forced the government to promise an investigation into the beatings. This concession, and Wałęsa's agreement to defer further strikes, proved a setback to the movement, as the euphoria that had swept Polish society subsided. Nonetheless the Polish communist party—the Polish United Workers' Party (PZPR)—had lost its total control over society.