Starting with Julio Argentino Roca in , ten consecutive federal governments emphasized liberal economic policies. The massive wave of European immigration they promoted—second only to the United States'—led to a near-reinvention of Argentine society and economy that by had placed the country as the seventh wealthiest  developed nation  in the world.
Driven by this immigration wave and decreasing mortality, the Argentine population grew fivefold and the economy fold: He enacted social and economic reforms and extended assistance to small farms and businesses.
Argentina stayed neutral during World War I. The second administration of Yrigoyen faced an economic crisis, precipitated by the Great Depression.
His liberation was forced by a massive popular demonstration , and he went on to win the election. He nationalized strategic industries and services, improved wages and working conditions, paid the full external debt and achieved nearly full employment. The economy, however, began to decline in because of over-expenditure. She pushed Congress to enact women's suffrage in ,  and developed an unprecedented social assistance to the most vulnerable sectors of society.
In the Navy bombed the Plaza de Mayo in an ill-fated attempt to kill the President. A few months later, during the self-called Liberating Revolution coup, he resigned and went into exile in Spain. Arturo Frondizi from the UCR won the following elections. Guerra Sucia was part of Operation Condor , originally planned by the CIA ,   and for which the United States government provided technical support and supplied military aid to during the Johnson , Nixon , Ford , Carter , and Reagan administrations.
The Dirty War involved state terrorism in Argentina and elsewhere in the Southern Cone against political dissidents, with military and security forces employing urban and rural violence against left-wing guerrillas, political dissidents, and anyone believed to be associated with socialism or somehow contrary to the neoliberal economic policies of the regime.
The guerrillas, whose number of victims are nearly — between military and police officials  and up to civilians  were already inactive in , so instead of a war the actual situation was a genocide practiced by the Junta over the civilian population. During this period, in which it was later revealed 8, "disappeared" in the form of PEN Poder Ejecutivo Nacional, anglicized as "National Executive Power" detainees who were held in clandestine detention camps throughout Argentina before eventually being freed under diplomatic pressure.
Trade unionists were targeted for assassination by the Peronist and Marxist paramilitaries as early as , and individual cases of state-sponsored terrorism against Peronism and the left can be traced back to the Bombing of Plaza de Mayo in In , popular discontent led to two massive protests: The terrorist guerrilla organization Montoneros kidnapped and executed Aramburu. He expelled Montoneros from the party  and they became once again a clandestine organization. They initiated the National Reorganization Process , often shortened to Proceso.
By the end of Montoneros had lost near 2, members; by , the ERP was completely defeated. A severely weakened Montoneros launched a counterattack in , which was quickly annihilated, ending the guerrilla threat.
Nevertheless, the junta stayed in power. Guerra de Malvinas ; within two months Argentina was defeated by the United Kingdom. Reynaldo Bignone replaced Galtieri and began to organize the transition to democratic rule. The worsening economic crisis and hyperinflation reduced his popular support and the Peronist Carlos Menem won the election.