By now, most Americans should be aware that the country is in the middle of a serious opioid addiction crisis. Drug overdose is now the leading cause of death for Americans under 50, two thirds of which are from opioid overdoses.

While approximately half the opioid overdose deaths are from prescription drugs, heroin use has also dramatically increased. A study from Columbia University found that heroin use among American adults has increased almost fivefold in the last decade.

The relationship between prescription drug abuse and heroin use is key to understanding the crisis. Often after getting addicted to a prescription opioid like OxyContin or Vicodin, a now-addict is cut off by a physician from legally obtaining an opioid drug. That person then moves to heroin, which is readily available on the black market and in high-quality form.

And where is all this high-quality heroin coming from? Afghanistan.

Since the U.S. invasion in 2001, opium production in Afghanistan has spiked – paralleling the spike in opioid use in the United States.

According to the United Nations Office on Drug and Crime, opium production has massively increased since 2001, hitting higher levels in 2016 from 2015.

This increased production has led to the U.S. (and other places) being flooded with cheap and very potent heroin.

Given the scale of the opium production in Afghanistan, it would be absurd to claim the U.S. government is somehow unaware of the activity. In fact, all available evidence suggests U.S. forces are tolerating the thriving opium trade in exchange for loyalty from Afghan political leaders – a process that, at one time at least, went all the way up to the president.

After the overthrow of the Taliban in 2001, the U.S. installed Hamid Karzai as president of Afghanistan. The president’s brother, Ahmed Wali Karzai, became one of the biggest opium dealers in Afghanistan to such a degree that U.S. officials felt the need to continually lobby President Karzai to get his brother under control or exile him.

As The New York Times reported in 2008:

The White House says it believes that Ahmed Wali Karzai is involved in drug trafficking, and American officials have repeatedly warned President Karzai that his brother is a political liability, two senior Bush administration officials said in interviews last week.

Numerous reports link Ahmed Wali Karzai to the drug trade, according to current and former officials from the White House, the State Department and the United States Embassy in Afghanistan, who would speak only on the condition of anonymity. In meetings with President Karzai, including a 2006 session with the United States ambassador, the Central Intelligence Agency’s station chief and their British counterparts, American officials have talked about the allegations in hopes that the president might move his brother out of the country, said several people who took part in or were briefed on the talks.

Ahmed Wali Karzai was assassinated in 2011, but the president’s family were hardly the only ones in the Afghan ruling class getting a taste of the profits from one of the country’s biggest exports.

Nor is this the first time the U.S. empire has tolerated opium dealing among its allies. As noted in the seminal work by Alfred McCoy The Politics of Heroin: CIA Complicity in the Global Drug Trade, U.S. intelligence agencies collaborated with major opium dealers in Laos and throughout Southeast Asia during the 1960s and 1970s in exchange for political support against “the spread of communism.”

A similar deal was made by the Reagan Administration in the 1980s with cocaine dealers in Central and South America. The CIA helped facilitate the importation of cocaine into Los Angeles by an anti-communist group known as the Contras (at the beginning of what would become the crack epidemic) in order to assist the Contras in their war against the socialist government of Nicaragua.

While there is a realpolitik argument for making alliances with drug dealers to achieve larger geopolitical goals, it does fundamentally undermine the moral preening associated with the so-called U.S. “War on Drugs.”

But if the U.S. government really wants to curtail the opioid crisis, it has at least one clear and obvious action it can take – stop the war in Afghanistan.