Cold War tensions began to have a noticeable impact on the political climate in Chile in late 1945 and early 1946 when Cold War rhetoric and postures helped to precipitate confrontation between the Chilean government and the Partido Comunista de Chile (PCCh) and division in the country's most powerful trade union confederation, the Confederation de Trabajadores de Chile (CTCh). However, it was not until late 1947 that Chile's Cold War struggles reached their climax in a coal miners strike that led, a year later, to the passage of the Ley de Defensa Permanente de la Democracia through Congress, a law that formally excluded Communist party members from participation in Chile's political and trade union life for more than a decade.

Because the PCCh was not an isolated sect on the margins of Chilean politics, but a major working-class party with deep roots in the political and trade union life of the country, the processes of confrontation and exclusion had traumatic repercussions. By the time the Ley de Defensa Permanente reached the statute book, the Center-Left coalition that the PCCh had done so much to create and sustain and that, since 1938, had helped to elect three successive presidents of the republic from the centrist Partido Radical (PR)-Pedro Aguirre Cerda, Juan Antonio Rios Morales and Gabriel Gonzalez Videla-was irrevocably destroyed. By that time too, the split inside the CTCh had become permanent and the trade union movement as a whole was cowed and contained.