information:filtering
Rise and fall of military dictatorships

Wars became less frequent in the 20th century, with Bolivia-Paraguay and Peru-Ecuador fighting the last inter-state wars. Early in the 20th century, the three wealthiest South American countries engaged in a vastly expensive naval arms race which began after the introduction of a new warship type, the " dreadnought ". At one point, the Argentine government was spending a fifth of its entire yearly budget for just two dreadnoughts, a price that did not include later in-service costs, which for the Brazilian dreadnoughts was sixty percent of the initial purchase.

The continent became a battlefield of the Cold War in the late 20th century. Some democratically elected governments of Argentina, Brazil, Chile, Uruguay and Paraguay were overthrown or displaced by military dictatorships in the 1960s and 1970s. To curtail opposition, their governments detained tens of thousands of political prisoners, many of whom were tortured or killed on inter-state collaboration. Economically, they began a transition to neoliberal economic policies. They placed their own actions within the US Cold War doctrine of "National Security" against internal subversion. Throughout the 1980s and 1990s, Peru suffered from an internal conflict.

In 1982, Argentina invaded the Falkland Islands, a British dependent territory. The Falklands War began and 74 days later Argentine forces surrendered.

Colombia has had an ongoing, though diminished internal conflict, which started in 1964 with the creation of Marxist guerrillas (FARC-EP) and then involved several illegal armed groups of leftist-leaning ideology as well as the private armies of powerful drug lords. Many of these are now defunct, and only a small portion of the ELN remains, along with the stronger, though also greatly reduced, FARC.

Revolutionary movements and right-wing military dictatorships became common after World War II, but since the 1980s, a wave of democratization passed through the continent, and democratic rule is widespread now. Nonetheless, allegations of corruption are still very common, and several countries have developed crises which have forced the resignation of their governments, although, on most occasions, regular civilian succession has continued.

International indebtedness became a significant problem in the late 1980s, and some countries, despite having strong democracies, have not developed political institutions capable of handling such crises without resorting to unorthodox economic policies. This was illustrated by Argentina's default in the early 21st century. There has been an increased push towards regional integration, with the creation of uniquely South American institutions such as the Andean Community, Mercosur and Unasur. Starting with the election of Hugo Chávez in Venezuela in 1998, the region experienced a pink tide – the election of several leftist and center-left administrations in most countries, except the Guianas and Colombia.