Like most other South American countries in the 1960šs, Argentina had a history of unstable governments. A high rate of urbanization (over 70%) and the general economic decline with its attendant unemployment and inflation throughout South America created social tension that was exploited by radical groups. Guerrilla movements were most active in Argentina from 1968 to 1977. A number of radicals who had been trained in guerrilla warfare in Cuba returned to Argentina and began to conduct a campaign of urban terrorism, robbing banks and attacking small military garrisons to collect money and weapons. One such group was called the Ejercito Revolucionario del Pueblo (ERP). It was created in 1969 as the "fighting arm" of the Trotskyist Revolutionary Workers Party. In 1970 another group called the Montoneros appeared. This leftist group was working for the return of Isabel Peron, the populist left-wing dictator who had been thrown out of Argentina by the military in 1955 into exile in Spain. The Montoneros had strong support from the organized trade unions (who had wielded considerable power during the reign of Peron) and often operated in conjunction with the ERP, despite their differing ideological backgrounds. Both groups relied more on ransoms from political kidnappings than bank robberies for financial support. They usually targeted representatives of foreign companies who had set up business in Argentina. In this way they could demand (and receive) large ransoms and please nationalistic Argentinians by 'attacking foreigners'. The sums demanded rose rapidly, from $1 million for a Fiat executive in 1972 to a high of $14.2 million paid in 1974 for an Exxon executive. Other large companies and airlines paid varying amounts of protection money to the ERP to ensure that they would be left alone. The ERP used this money to finance its operations, used some of it to buy medical supplies, food, and clothing for the poor of Argentina, and wisely invested the rest (at one point, the interest alone from their invested ransoms was $130,000 a month). The Montoneros asked for and got one of the largest ransoms in history by kidnapping the two sons of Jorge Born, chairman of one of Argentinašs largest companies. They demanded $60 million in cash and that $1.2 million worth of food and clothing be given to the poor. In 1974 and 1975 the ERP continued to kidnap and assassinate selected figures in Argentinian society (successful hits included the Chief of Police for all Argentina and their head of Defence Intelligence) and to raid military bases in search of weapons and kidnap victims. There were several raids involving 50-100 guerrillas, and the largest operation of this type was an attack in December 1975 on a military arsenal south of Buenos Aires involving almost 500 guerrillas. The attack was repulsed with 85 guerrillas killed and most of the remainder captured. An attempt to set up a 'rural liberated area' in the sparsely populated north of Argentina in 1974 and 1975 was thwarted by the Army, and the ERP lost almost 600 guerrillas in three months. After these setbacks, the ERP and Montoneros returned to an urban campaign of smaller-scale raids, bombings, assassination, and sabotage. In March 1976 the military seized power in Argentina. The junta led by General Jorge Videla immediately started the 'dirty war' against terrorism, in which between 10,000 and 20,000 people are believed to have been killed. Both regular units of the armed forces and vigilante organizations such as the 'Triple A' (Argentinian Anticommunist Alliance) used indiscriminate counter-terror to break the back of the terrorist groups and stifle domestic opposition. They relied on mass arrests, torture, and executions without trial, the bodies being left literally in heaps on the streets of Buenos Aires as an example to the terrorists not yet caught. The Montoneros, who at one time had numbered as many as 7,500 effectives, were dispersed. The ERP was also scattered. Once again, a campaign of urban terror had forced the government into severe repression, but no popular revolutionary movement arose to overthrow the government. As in Uruguay, the military government that came to power smashed the terrorist movements and silenced opposition so effectively no such reaction was possible.