Violent clashes in Colombia between the military and protesters, many angry over tax increases on the poor, since early May reflect a continued breakdown of Colombian society. A 2016 peace process brought an end to armed conflict after more than 50 years. But over the past two years, leftist forces — including the Revolutionary Armed Forces of Colombia, or FARC, and the National Liberation Army, or ELN — have reemerged to demand political power and control. Conservative opponents, their right-wing paramilitary organizations and government forces have responded forcefully. The drug cartels, many aligned with both sides, continue their reign of terror. In between, many Colombians again find themselves trapped in a cycle of violence.

But the United States has also played a substantial role in this conflict, by providing the military equipment now being used by security forces to forcibly quell dissent. Starting under the Lend-Lease Act during World War II, U.S. military strategy focused on providing aid to anti-communist regimes throughout the world. During the 1990s, that policy combined with efforts to stop the flow of cocaine and heroin into the United States, ultimately militarizing security forces in Latin American countries. The consequences of this strategy are now fully on display in the streets of Colombia — and being borne by Colombians.

Starting before World War II, the United States developed a strategy of arming allies and becoming what President Franklin D. Roosevelt called the “arsenal of democracy.” This continued in the Cold War as the fight against communism led to continued military support for allies, including totalitarian ones.

The trend escalated in the late 1990s with the implementation of Plan Colombia. President Andrés Pastrana proposed a “Marshall Plan” for Colombia in 1999 to stop the production of coca and opium by uplifting peasants reliant on the crops. The Clinton administration approved the concept, hoping to balance security and counternarcotics operations with social and economic development. The continued civil war and burgeoning drug trade pushed the United States to heighten its interest in the country, despite the absence of Cold War imperatives.

However, from the beginning the majority of aid went to the security forces — over 75 percent of the nearly $2 billion in the first year. Soon, American military advisers poured into the country, including 500 in the year 2000, following a pattern over many years of relying on military solutions rather than the infinitely more complex economic and social ones.

The George W. Bush administration expanded the initial effort, focusing on crop eradication as well as counterinsurgency against the FARC and ELN. These Marxist-oriented groups had operated since the 1960s and had long sought to overthrow the government and follow Cuba’s example. But the 9/11 attacks changed the U.S. perspective, and the Bush administration increasingly tied the battle against the FARC and ELN to the global war on terrorism. At the same time, U.S. policymakers expanded efforts to fight the drug cartels, justifying many actions as a continuation of the war on drugs. By 2003, an estimated 5,000 U.S. soldiers and contractors worked from the U.S. Embassy in Bogota, a much larger force than any place outside Iraq and Afghanistan.

Military hardware flooded the country, including state-of-the-art military equipment and even “smart bomb” kits (highly advanced guided bombs) that targeted FARC and ELN leaders. As The Washington Post’s Nick Miroff reported in 2016, Plan Colombia “gave the country a vast, sophisticated intelligence-gathering system to hunt the rebels, as well as the lethal hardware to strike them from the skies.” The Colombian security forces became the best-armed in the region, flying Black Hawk helicopters into combat along with using other advanced hardware. Often these same forces did little to differentiate rebels, drug lords and the civilian population, leading to documented atrocities.

For the most part, U.S. leaders portrayed the operations as counternarcotics measures. The United States provided aerial pesticides and manual means of destroying crops. Colombian security forces, aided by U.S. intelligence, also concentrated on laboratories and other facilities used to produce narcotics.

As a counterinsurgency, Plan Colombia was effective, and the FARC and ELN came to the negotiating table and reached agreements in 2016 to disarm and join the political structure of the country rather than seeking its violent overthrow. But the implementation of the peace plan faltered and the groups reignited their insurgency with an eye toward seizing power. Violence has followed, including an attack on the national police academy by the ELN in January 2019 that killed 22 people and wounded many others.

Plan Colombia’s aim to undermine drug production had more-limited successes. The number of hectares of coca production shrank, but $4.5 billion remained in Colombia’s drug-related economy, according to the Brookings Institution. It curtailed drug production but left rural people highly impoverished. “Alternative livelihood programs … have with few exceptions been poorly implemented by the Colombian government,” the Brookings report stated.

The operations also resulted in many civilian deaths, similar to those in Guatemala and El Salvador in the 1980s. Often, Colombian military sources shared the intelligence gathered by the CIA and U.S. Defense Department with right-wing paramilitaries that committed numerous atrocities, including against human rights and labor activists. “The military was able to outsource violence to the paramilitaries,” Winifred Tate, author of a critical history of Plan Colombia, told The Post in 2016. “So they were not directly accountable, but it was still a fundamental part of counterinsurgency strategy.”

Ultimately, nearly $10 billion of U.S. aid flowed into Colombia between 2000 and 2016, the vast majority for security forces. In the aftermath of the 2016 peace, U.S. policymakers, including President Barack Obama, praised the successes of Plan Colombia and argued for its replication elsewhere, including in Mexico and Central America.

The unintended although not unsurprising fact was that because of U.S. policy, the security forces became more militarized and brutalized Colombian people. What we are seeing today in the response to protests is part of this outcome, with police and state forces using lethal force on citizens. For people already caught in the midst of rebels, drug cartels and gangs, and right-wing paramilitaries, the heavily armed Colombian military and police form another level of repression.

Thus, Plan Colombia reveals the link between violence and U.S. foreign policy. The heavily armed and often violent Colombian security forces in the streets this year have made it obvious that the long-term effects of arming them continue to be a major threat to stability in the country. But as is often the case, short-term gains outweigh the thought of considering the long-term effects in U.S. military and foreign policy.