The FARC imposed a 'tax' on coca paste, the substance produced by farmers like Montiel.
Guerima, Colombia: Isidro Montiel arrived in Colombia's lawless "drug triangle" in 1982 hoping to get rich farming coca, the raw ingredient for cocaine.
Today, with the country perched at the edge of a new era, he is betting instead on cacao, the little brown seeds used to make chocolate.
"I had heard that planting coca was a good living," Montiel, a stout 57-year-old farmer, said of his decision 35 years ago to move to the remote triangle of jungle between the villages of Guerima, Chupave and Puerto Principe, in the eastern department of Vichada.
Back then, notorious drug lord Carlos Lehder was building clandestine airstrips across this territory, which is roughly the size of Iceland, to fly cocaine to the United States.
Demand in the US was booming, and "a huge amount of cocaine was being shipped by air," said Colombian air force commander Jean Paul Strong, who heads a special task force in the region.
Word quickly spread around Colombia that Lehder -- the co-founder of the Medellin Cartel, along with Pablo Escobar -- needed workers to build this cocaine empire.
But soon after Montiel arrived, the situation took a dramatic twist.
Escobar tipped off authorities to Lehder's whereabouts, leading to his arrest and extradition to the United States in 1987.
That left a power vacuum in the triangle that was soon filled by the Revolutionary Armed Forces of Colombia, or FARC, a Marxist guerrilla group at war with the government since 1964.
The FARC imposed a "tax" on coca paste, the substance produced by farmers like Montiel.
Taking a cut of the lucrative drug trade quickly became one of the rebels' main funding sources, along with ransom kidnappings.
Drugs and violence
In Colombia, the world's top cocaine producer, that nexus between leftist rebels and drug traffickers has fueled a half-century conflict that has killed more than 260,000 people and left 60,000 missing.
It also translated into a bleak reality for farmers like Montiel.
"It was humiliating. It was either pay up or pay up -- no alternative. It's not right, having to work and then give away your product," said Montiel.
He said the FARC used to extort more than 30 percent of the $760 he made on each kilo of coca paste.
But then history shifted beneath his feet again.
In 2012, the FARC entered peace talks with the government, eventually signing a historic peace deal that saw the rebels begin laying down their arms this week.
That same year, Montiel signed up for a new government program to encourage coca farmers to switch to legal crops.
It subsidizes cacao farming, and also gives producers direct deals with chocolate manufacturers so they can sell at the market price -- no middleman to take a cut.
That has made cacao even more profitable than coca -- and a lot less risky.
Farmers say they make up to $1,700 for each of their two annual cacao harvests under the program.
With coca, which had to be harvested four times a year, they made between $275 and $840 annually.
The ones who make money (on coca) are the drug traffickers," said Jesus Sanchez, 59, who spent 16 years farming coca.
Coca paste is still used as currency in the triangle, where stores sometimes accept it instead of cash. Lunch costs five grams of coca paste, or the equivalent of about $3.50.
But cacao is gaining ground.
Today, 240 families are enrolled in the crop substitution program.
Colombia hopes such programs will convince farmers to switch away from coca on 50,000 hectares of fields this year.
Under the peace deal, demobilized FARC fighters are to be enlisted to promote the initiative in the country's most war-torn areas.
The effort kicked off last month in Vichada and Caqueta, another region hit hard by the conflict.
In Vichada, where there were 10,000 hectares (25,000 acres) of coca fields in 2002, there are just 683 today.
The goal is to have the number down to zero in three years.
But insecurity still dogs the region.
Residents complain they still have to pay "vaccines," or extortion money, to criminal gangs -- an indication of the treacherous path ahead for Colombia as it seeks lasting peace.