Around the region, many such groups have been hunted down or incorporated into leftist political parties as military dictatorships gave way to democracies and dissent began emerging in different forms. Even where guerrillas persist, they are significantly winnowed down, like the Shining Path in Peru, or pursuing peace talks with the government, like the Revolutionary Armed Forces of Colombia.

Then there is Paraguay, one of Latin America’s poorest and most unequal nations. Even as the economy booms, the Paraguayan People’s Army is evolving from a ghostlike irritant for the authorities in Asunción, the capital, into a broader security threat in a backcountry that is already a hub for traffickers of marijuana, defiantly cultivated here on sprawling plantations, and Andean cocaine smuggled into Brazil and Argentina.

Nearly everything about the Paraguayan People’s Army is in dispute, from its size to its ideology, with an important exception: The group’s operations are intensifying this year, building on a slow-burning insurgency in areas where the guerrillas are thought to draw support from impoverished farmers chafing at the expansion of large-scale soybean farms and cattle ranches.

The group is carrying out attack after attack on isolated police and army posts, while pursuing targeted killings of peasants accused of collaborating with security services. Bivouacking in the dense remnants of the Atlantic Forest that once blanketed much of Paraguay, it has eluded every military campaign aimed at eradicating it.

While the official estimates of victims killed by the group remains relatively low, numbering in the low dozens, pockets of northern Paraguay have nevertheless taken on the semblance of a war zone as the central government ramps up military patrols and deploys special operations units to find the guerrillas.