The ZOMO gained the most of their infamy during the period of martial law in Poland (1981–1983). During this time period their brutal actions against peaceful protesters often affiliated with the oppositionist Solidarity movement, and the subsequent lack of prosecution of those responsible for deaths of protesters, were major factors in bringing down the communist regime. To parody the communist newspeak during that time they were often sarcastically called "The beating heart of the Party" (pl. "Bijące serce Partii"). Since 1990 several trials against former ZOMO members and their political leaders took place, most prominently in the case of the massacre in the Wujek Coal Mine (where nine people were killed and 21 wounded when Katowice's Special Platoon opened fire on the striking miners in 1981 in the bloodiest incident of the martial law era).