Menzies came to power the year the Communist Party of Australia had led a coal strike to improve pit miners' working conditions. That same year Joseph Stalin's Soviet Union exploded its first atomic bomb, and Mao Zedong led the Communist Party of China to power in China; a year later came the invasion of South Korea by Communist North Korea. Anti-communism was a key political issue of the 1950s and 1960s. Menzies was firmly anti-Communist; he committed troops to the Korean War and attempted to ban the Communist Party of Australia in an unsuccessful referendum during the course of that war. The Labor Party split over concerns about the influence of the Communist Party over the Trade Union movement, leading to the foundation of the breakaway Democratic Labor Party whose preferences supported the Liberal and Country parties.