Jaruzelski was chiefly responsible for the imposition of martial law in Poland on 13 December 1981 in an attempt to crush the pro-democracy movements , which included Solidarity , the first non-Communist trade union in Warsaw Pact history .
Jaruzelski imposed martial law in Poland on 13 December 1981 to stop pro-democracy movements including Solidarity , the first non-Communist trade union in the Warsaw Pact .