Overseas, however, the U.S. approach to drugs still looks a lot like war. The D.E.A., assisted by the U.S. military, acts as an international police force, coördinating with foreign militaries through a network of offshore bases. Of the twenty-five billion dollars that the federal government spent fighting drugs last year, forty per cent went to treatment and prevention programs. The rest went to “supply reduction.” In Mexico, the $1.9 billion Mérida Initiative has relied on an enforcement-driven strategy somewhat similar to Plan Colombia’s. In 2006, President Felipe Calderón decided to deploy the Mexican military to fight drug cartels; since then, more than seventy thousand people have been killed in drug-related violence. Another twenty-six thousand people were reported missing. At least ninety per cent of U.S.-bound cocaine continues to move through the country. In Washington, one of Mérida’s most prominent faces is Assistant Secretary of State William Brownfield, formerly Ambassador to Colombia and Venezuela, who was also instrumental in organizing Operation Anvil. In June, Brownfield told a Senate subcommittee that the criteria for judging Mérida’s success should shift from “inputs” (aircraft, equipment, and training) to “outputs” (homicide rate, conviction rate, interdictions). “If the endgame is perfection, we’ll never get there,” Brownfield said. “At least, not in this world.”

In Congress, some are losing patience. “There is great fatigue surrounding our drug programs in the Western Hemisphere,” a staff member told me. “We don’t have good ideas. We don’t have good answers. We don’t have good anything. But we also know that doing nothing is a problem. So the whole thing is on autopilot. When you’re in the machine, it’s very difficult to say anything other than ‘Keep shooting. Keep decapitating the cartels.’ ”

“The war on drugs has simply not worked,” George P. Shultz, who served as Secretary of State under Reagan, told me. “It hasn’t kept drugs out of this country.” In 2011, Shultz, along with a committee of former heads of state, businessmen, and retired U.S. officials, called for an overhaul of U.S. drug-enforcement policy. The effects of interdiction programs like Anvil, they wrote, “are negated almost instantly,” wasting money that would be better spent on treatment and harm reduction. I asked Shultz why ineffectual policies have persisted. “We haven’t felt the full effects of it ourselves,” he said. “It took us twelve years to learn that Prohibition wasn’t working. There was Al Capone, there was the St. Valentine’s Day Massacre. The violence was here. Now we have outsourced the violence, in effect, to Mexico and Guatemala and Honduras.”