A few years ago, one of the greatest risks of driving through Colombia’s southern Guaviare region was getting a tire hopelessly stuck in the mud along its tortuous, unpaved roads. A former stronghold of leftist insurgency, Guaviare shook off decades of rebel control in 2016, when Bogotá signed a peace deal to demobilize the Revolutionary Armed Forces of Colombia, or FARC. Rural residents looked on in hope and disbelief as police, rather than guerrilla fighters, patrolled their towns. Peace, it seemed, had finally arrived.

Less than a decade later, that peace is gone. Land mines line many of the muddy byways. Residents clutch unofficial ID cards mandated by armed groups to distinguish friends from enemies. “There are three options now,” a young community leader told me recently. “Either you do what the armed group says, you leave, or they kill you.”

Guaviare’s short-lived tranquillity is part of an alarming deterioration in security across Colombia. The 2016 peace agreement ended half a century of war and dramatically reduced violence. As guerrilla fighters handed over their weapons, nationwide homicide rates — once among the highest in the world — fell below those of many American cities. Many former FARC members, who for decades used the drug trade to finance their rebellion, left cocaine trafficking behind.

Colombia today is still far from the brutal chaos of the 1990s and early 2000s. But a new host of armed groups has expanded and multiplied across the country, fueling an explosion in violent crimes ranging from extortion to kidnapping and child recruitment. The assassination this summer of the presidential hopeful Miguel Uribe Turbay and a recent wave of terrorist-style bomb and drone attacks augur further violence ahead of the 2026 elections.

Colombia’s return to conflict is not proof that the 2016 deal failed, but a lesson in how hard it is to sustain progress toward peace. The government has struggled to control the regions that the FARC left behind, and new criminal groups have since retaken lucrative drug and human trafficking routes. To regain that lost ground, Colombia needs to return to the principles that so successfully reduced violence in the first place: dialogue, measures to remedy the inequality and political exclusion that provide a foothold for criminal activity, plus a strong security strategy to pressure armed groups.

The backslide into violence has multiple origins. Although the FARC was formally disbanded in a matter of months, political battles over contentious parts of the agreement, such as transitional justice and victims’ rights, have dragged on for years. The state’s bureaucracy was unprepared for the challenges of following through on some of its more complex commitments, such as addressing rural inequality, weaning farmers off coca cultivation and ensuring political rights for all Colombians.