BOGOTÁ, Colombia — It was a 58-year conflict, involved almost every sector of Colombian society, and cost hundreds of thousands of lives and billions of American dollars.
And on Tuesday, a government-appointed truth commission released the most comprehensive examination yet of Colombia’s brutal internal conflict, which spanned 1958 to 2016.
The report was highly critical of the security model that dominated the country for decades, which the authors said treated much of the population as internal enemies, and it called for sweeping transformation of the police and military.
It also delivered a sharp rebuke of United States policy in Colombia, saying that mounting a war against drug trafficking had disastrous social and environmental effects, turning poor farmers into enemies of the state and poisoning once fertile landscapes.
“The consequences of this concerted and largely U.S.-driven approach,” the report said, led to a “hardening of the conflict in which the civilian population has been the main victim.”
Declassified documents used to compile the report, which were obtained by The New York Times, show that Washington believed for years that the Colombian military was engaged in extrajudicial killings and was working with right-wing paramilitaries, and yet continued to deepen its relationship with the armed forces.
The report, which was four years in the making and involved more than 14,000 individual and collective interviews, was a product of the 2016 peace deal between the Colombian government and its largest rebel force, the Revolutionary Armed Forces of Colombia, or FARC. It is meant to aid in healing after the war, and included a new estimate of the dead: 450,000 people, nearly twice the number previously believed.
At a ceremony marking the report’s publication, some victims cried in their seats, while others shouted for recognition for their loved ones. Some of the commissioners, who were responsible for creating the report, wore T-shirts that read: “There is future if there is truth.”
The list of victims “is unending and the accumulated pain is unbearable,” the Rev. Francisco de Roux, who led the truth commission, told a packed theater in downtown Bogotá, the capital. “Why did we watch the massacres on television, day after day, as if they were a cheap soap opera?”
But the report quickly become part of a highly polarized political landscape in Colombia, in which some believe the military was complicit in war crimes and needs systemic reform and others blame leftist guerrillas for most of the trauma.
President Iván Duque, a conservative who campaigned against the peace deal and who is known for an unwavering defense of the military, did not attend the ceremony or comment publicly on the report.
His party, the Democratic Center, released a statement referring to the report as an “interpretive truth.”
President-elect Gustavo Petro, who in August will become the country’s first leftist president, attended the ceremony with Vice President-elect Francia Márquez. Mr. Petro has promised to make Colombia’s peace deal a priority, and called on the campaign trail for military reform.
Mr. Petro told the audience he believed that the report could help “end, definitively, the cycles of violence” the country had suffered for generations, but that that could happen only if the report was not used as a weapon for vengeance.
Societies will always have conflict, he said, “but conflict cannot be synonymous with death.”
Pastora Mira García, 65, whose father was killed in the war, had traveled more than 200 miles to attend the event. She called the report’s release “a very hopeful moment for our country.”
The Colombian conflict began as a war between the government and the FARC, but eventually evolved into a complex battle that also involved paramilitary groups and the U. S. government, which provided billions of dollars in aid to the Colombians to help them fight the insurgency and the drug trade that funded it.
The report will eventually consist of 10 chapters; two of those chapters were released Tuesday, including an 896-page summary of findings and recommendations for the future.
The summary gives a detailed account of suffering, inflicted most often on civilians, documenting massacres, forced disappearances, extrajudicial killings, kidnappings, extortion, torture, sexual assault and child recruitment, among other human rights violations.
Those crimes, the report said, were committed by the FARC, by paramilitaries, by state security forces and by others.
Among the commission’s recommendations for the police and military are increased oversight and accountability; restructuring of the state security forces that removes the national police from the defense ministry; moving the cases of members of the military accused of crimes to the civil justice system, from the military one; and elimination of agreements between the military and private companies in which state security forces are paid to protect private entities, like oil companies.
“These are very important proposals,” said Juan Carlos Ruiz, a political scientist at Rosario University in Bogotá who studies the Colombian police.
Calls for change have existed for years, he said, but have never been successful.
Among the evidence used to write Tuesday’s report were thousands of declassified U.S. documents gathered and organized by the National Security Archive, a Washington-based nongovernmental organization that specializes in supporting post-conflict truth commissions.
A digital library of the documents will be published in August, but the National Security Archive provided The Times with some ahead of time. They reveal that the United States had decades of knowledge of alleged crimes committed by the Colombian military — “and yet the relationship continued to grow,” said Michael Evans, director of the Archive’s Colombia project.
Particularly noteworthy, he said, are a series of C.I.A. operational reports not normally available to the public, even after a record request.
One report, written in 1988 during a period in which leftist activists were being killed on a regular basis, found that a wave of assassinations carried out against “suspected leftists and communists” was the result of “a joint effort” between the intelligence chief of the Colombian Army Fourth Brigade and members of the Medellín narcotics trafficking cartel.
Many of those killed were associated with a political party called the Patriotic Union. The report said it was “unlikely” that this took place “without the knowledge of the Fourth Brigade commander.”
Later in the document, a C.I.A. officer writes of a 1988 massacre in which 20 farmworkers, many of them union members, were killed. The C.I.A. officer indicates that the U.S. government believed the assassins “obtained the names of their intended targets” from the Colombia Army’s 10th Brigade intelligence unit.
Other documents show that the United States knew oil companies were paying paramilitaries for protection, and that at least one company gathered intelligence for the Colombian military.
One company was “actively providing intelligence on guerrilla activities directly to the Army,” according to the C.I.A., “using an airborne surveillance system along the pipeline to expose guerrilla encampments and intercept guerrilla communications.”
The Colombian Army “successfully exploited this information and inflicted an estimated 100 casualties during an operation against the guerrillas” in 1997, according to the report.
Another document, written in 2003, hints at one of the grimmest chapters of the war, called the false positives scandal. In that case, the Colombian military is accused of killing thousands of civilians during the presidency of Álvaro Uribe and trying to pass them off as combat deaths, in an effort to show that it was winning the war.
In recent court testimony in Colombia, former soldiers have said they felt pressured by higher-ups to kill fellow Colombians.
A July 2003 memo to Donald Rumsfeld, then the secretary of defense, from the top Pentagon deputy for special operations, celebrates a significant rise in combat kills since Mr. Uribe took office took — 543 in just six months, compared with 780 during the last two years of the previous government.
The document is titled “Recent Successes Against the Colombian FARC.”
Iñigo Alexander contributed reporting from Bogotá, Colombia.