The United States' war on drugs isn't just doing damage within the US: it's helping to drive appalling atrocities in Mexico and Central America. Torture, forced disappearances, violence used to silence and punish dissent — these are crimes most commonly associated with civil wars, brutal dictatorships, or terrorist insurgencies. But drug cartels and criminal gangs are using those same tactics throughout much of Central America today, as a direct result of American policies in the war on drugs.

You may have heard, most recently, about the excavations of mass graves in Mexico, in search of 43 college students who ware missing, presumed murdered, for political reasons. Or about the child migrant crisis originating in Central America. On the surface, the two are not obviously connected. But both are directly linked to criminal drug violence. And that drug violence exists in no small part because the US war on drugs helped push it there.

How the US war on drugs fuels violence internationally

Cartel violence is fueled by a number of factors — insecurity in the affected areas, government corruption, and of course the depravity of the cartels themselves — but also by the United States' war on drugs.

Drugs are illegal, which leaves the markets for them to be dominated by criminals. Because the US drug market is so huge, access to it is worth killing for — which criminal organizations are willing to do.

The most lucrative way for criminal groups to access that market is to control smuggling routes. But to do so, cartels have to defend them not just against invasion by other cartels, but also against interference from police and from citizens who oppose the cartels' activities. In order to maintain that control, cartels rule through fear, using torture, threats, and murder.

Officials in Iguala, Mexico, are exhuming mass graves filled with charred, dismembered corpses

As part of the war on drugs, the US operates a range of programs to encourage other nations to crack down on drug traffickers, including support for military operations, funding for police, and more direct operations such as extraditions of cartel leaders to the United States for trial and imprisonment.

But those policies never actually end the drug trade or drug-related violence. Rather, they simply push that violence out of one area and into another, by forcing traffickers into weaker, more vulnerable countries that are even less equipped to combat them. The nature of the US war on drugs means that drug organizations are forced to find areas where they can operate with impunity, or to create those conditions locally by bribing or intimidating local government to the point of brokenness.

Once there, they flourish like an infection in an open wound, doing tremendous damage at almost every level of society.

When the US went after groups in Colombia, it ensured their rise in Mexico and the Northern Triangle

The past few decades have seen that process play out over and over again. In the 1990s and 2000s, for example, Colombia upped efforts to crack down on its powerful trafficking organizations, with a great deal of US help. But because the US had neither ended American consumers' demand for narcotics nor fundamentally altered the policies of its war on drugs, the Colombian traffickers were simply replaced by new crews of ultra-violent criminals in Mexico, where they have wreaked almost indescribable havoc.

Now that Mexico has been putting more pressure on its drug cartels, again with extensive help from the US, smuggling activity has shifted to the countries of the Central American "Northern Triangle": Guatemala, Honduras, and El Salvador. These countries, still reeling from the civil wars of the 1980s and '90s, proved to be hospitable environments for the cartels, which have greatly compounded the problems there.

This is a vicious cycle: state weakness allows the illicit drug trade to thrive. That illicit trade, in turn, increases corruption, as criminal organizations use bribery and threats to avoid police or government interference with their operations. That corruption further weakens state institutions, giving the criminal groups even more space to operate.

That state weakness also encourages other armed groups to flourish, such as criminal gangs and vigilante "self-defense" organizations. Gangs like M-18 and Mara Salvatrucha have flourished in the Northern Triangle countries. In recent years, as drug-trade-fueled corruption has has further weakened state institutions, the maras have been able to operate with impunity, growing especially powerful. Gang violence, extortion, and forced recruitment became so rampant and so destructive in schools that thousands of children and teens fled the region entirely, fearing for their lives, and ended up as migrants on the US-Mexico border.

The end result: mass graves and a faceless corpse in Mexico

Right now, officials in Iguala, Mexico, are exhuming mass graves filled with charred, dismembered corpses. They are searching for 43 student protestors who disappeared on September 26, and are believed to have been murdered by a drug cartel at the behest of corrupt local officials. Shortly after the attack, the body of one of the students was found with his eyes gouged out and the skin from his face removed. His companions remain missing.

Although police have identified multiple pits filled with bodies in the area, the remains found thus far have turned out to belong to other nameless victims, not the missing students. (You know things are bad when an investigation has to begin with the question "which mass grave?")

The disappearance of the 43 students has made international headlines, but they are only the latest appalling episode of violence in Mexico's drug war, which Human Rights Watch estimates claimed 60,000 lives between 2006 and 2012 alone. The killings are often flamboyantly violent, designed to terrify entire communities, not just eliminate cartels' immediate enemies. This month, for instance, cartel hit men live-tweeted the murder of Maria del Rosario Fuentes, a citizen journalist who had criticized them.

Nor are such attacks limited to Mexico. In Guatemala, Honduras, and El Salvador, violence committed by drug cartels and the gangs with which they collaborate has produced some of the highest murder rates in the world. The International Crisis Group has referred to the smuggling routes along the Guatemala-Honduras border as a "corridor of violence," where murder and other crimes cluster along the path of drugs heading towards the United States.

The problem is so bad that it can no longer be contained by national borders: between late 2013 and the middle of this year, more than 68,000 unaccompanied children fled north to escape the violence that was targeting their homes and schools, causing a refugee crisis on the United States' own southern border. While the American policy response to this has mostly been to ask what we should do with the children who arrive, it's also worth asking how things got so bad in their home countries that they would attempt such a dangerous trip, what role the US has played in helping to create those crises.

There has been and doubtless will continue to be much debate within the US over what the war on drugs does to Americans. And yet, these debates on the merits of the drug war too rarely consider its substantial death toll abroad. Even opponents of drug prohibition tend to focus on its costs here at home: communities crippled by mass incarceration, large-scale theft in the name of "asset forfeiture," police militarization, gang violence.

Those domestic problems are serious, and they would, on their own, be grounds for changing US policies. But they are not on their own. The war on drugs is empowering monsters and endangering the innocent from Texas to Tegucigalpa. That needs to end.