UP also initially included the moderate Party of the Radical Left, but in 1972 it joined the opposition (inside the Confederation of Democracy).

The loose and conditional support from the Christian Democratic Party that made this confirmation possible soon disintegrated, as did centrism of any viable kind in an atmosphere of increasing political polarization.

The Revolutionary Left Movement clashed with the conservative and establishment forces, while armed right-wing elements plotted to destabilize the government with support from the Nixon administration.

[1][2] The Pact of Popular Unity (Pacto de la Unidad Popular) was signed on 26 December 1969 in Santiago by following representatives of political parties: In August 1973 the Christian Democrats cooperated with the right-wing National Party in the congressional protest that set the stage for the Chilean coup of 1973, the effective end of the UP government and —for 17 years— of democracy in Chile.

In contrast with Fidel Castro's armed people's revolution, Allende proposed a peaceful and legal transition to socialism respecting the constitutional order.

The political violence exploded during 1973 with a first attempted coup d'Etat on 29 June and the assassination of Arturo Araya Peeters, aide-de-camp of Allende, the 27 July.

Finally, anti-socialist elements in the military, with support from US intelligence agencies, orchestrated a successful coup d'état on 11 September 1973.

This included mining of copper, nitrate, iodine, iron, and coal; the country's financial system, especially private banks and insurance companies; foreign trade; production and distribution of electricity; air, rail, and maritime transportation; all petroleum-based goods; iron, steel, cement, and paper.

Others followed over the next several months, and the opposition congress unanimously approved a constitutional reform for the nationalization of copper and other resources, expropriating large foreign companies without compensation.

One large difference between Christian Democrat and Popular Unity governments was their reactions to tomas, or seizures of land by the peasants.

A series of programs, including pay equality, resulted in diminishing incentives to work, and productivity fell.