The firing of a Gdansk shipyard worker in 1980 triggered a "butterfly effect" that led to the collapse of the Soviet empire, the prime minister said on Thursday. Mateusz Morawiecki was speaking at the 30th-anniversary congress of Solidarity. A worker, Anna Walentynowicz, was fired on August 8, 1980, five months before retirement, for her involvement in the union movement. Her sacking sparked a massive strike a week later, eventually leading to the establishment of the Solidarity movement.