The rebellion and its bloody aftermath ushered in a era of military rule as the oligarchy, desperate to defend its interests, handed political power to the army while retaining economic control. For the next fifty years the two groups worked together in a symbiotic relationship. Successive groups of tandas - cliques of military officers - assumed power, felled by coups and counter-coups as factions within the military itself fought for supremacy. The economic business of state was handled by the oligarchy, who relied on the army to protect its interests. Depending on the faction in power, occasional limited social reforms were made, although leaving the fundamental structures unchanged. A number of political parties were allowed to operate, but elections were widely perceived as a sham.

After World War II , economic interests diversified into production of sugar, cotton and beef for export. During the 1960s and 1970s, some limited industrialization also occurred. Needless to say, the profits and benefits deriving from this expansion remained firmly in the hands of the oligarchy, with social inequalities unchanged. The vast majority of the population had no access to land and - at best - only tenuous means of survival. The census of 1971 recorded that 64 percent of agricultural land was held by 4 percent of landowners, while two-thirds of rural families had either no land or worked plots that were insufficient to provide daily needs.

A downturn in export markets in the 1970s again led to a steep deterioration in conditions, with a subsequent increase in militant pressure for change. The elections of 1972, won by the Christian Democratic Party (PDC) led by José Napoleón Duarte , should have signalled a mandate for democratic change. The PDC advocated a peaceful road to reform, but following the election the army installed its own candidate, Colonel Arturo Molina , as president. Duarte and other opposition leaders were exiled, the National University closed down and trade union and reform activists persecuted and killed.

The cycle of repression continued throughout the 1970s as Molina's successor, Carlos Humberto Romero , took power in elections, again rigged, in 1977. Shortly after Romero took office, news programmes around the world showed footage of the army firing upon unarmed civilians during a protest in front of the cathedral in central San Salvador on February 28 - as many as three hundred people died. In 1979 the ineffectual Romero was himself deposed in a coup, replaced initially by a civilian military junta and then by a group of hard-line army officers in January 1980. The army accepted an offer from Duarte to form a provisional government on condition that certain reforms be introduced, yet repression continued, culminating in the assassination of Archbishop Oscar Romero on March 24, 1980 - a murder planned by serving army officer Roberto D'Aubuisson. Though preliminary reforms were implemented and agreement secured for a transfer of power from military to civilian hands, these were insufficient to halt a deepening cycle of extra-judicial violence.

The developments of the 1970s and continuing military domination had convinced many that change could only come through violence. Far-right paramilitary death squads waged campaigns of terror in the countryside and against those advocating reform. At the opposite end of the spectrum, left-wing guerrilla groups were mobilizing and advocating radical change. Archbishop Romero's assassination signalled the point from where descent into civil war became inevitable