Things change, usually for the worse, and always against the innocent. (This truth is a principle of curmudgeonry.) When I came to Mexico some eight years ago, it was a peaceful, moderately successful upper-Third-World country—middle-class, barely, literate, though often barely, and as democratic as the United States, which is to say barely. Things were improving, though often they had a long way to go. The young were visibly healthier than preceding generations. The birth rate was in sharp decline. Women entered the professions in substantial and growing numbers.

And it was safe. Expats sat over coffee at the plaza laughing at people back in the States, insular, fearful, ignorant of the world outside their borders. (For recent college graduates, Mexico is a country south of the United States. “South” is down on maps.) Mexico, they believed, was most astonishing perilous. Don't drink the water, avoid ice. Salads were thought especially lethal. The Federales would kill you for sport, like squirrels. On any given day, you would probably be shot several times by bandidos. It was nonsense.

Then Vicente Fox left office, and Felipe Calderon came in. He declared war on the narcotraficantes. Why he did this, I don't know, since Mexico didn't have a drug problem. My guess is that Washington pushed him into it, but I don't know.

Unfortunately Mexico, which neither produces nor uses a lot of drugs, lies between Colombia, which produces vast amounts of drugs, and Americans, who want vast amounts of drugs. Washington does not want Americans to have vast amounts of drugs. Neither did it want to lose votes by imprisoning white users of drugs, such as college students, high-school students, professors, Congressmen, lawyers, and blue-collar guys driving bulldozers. The answer was to make Mexico fight Washington's wars.

But Mexico couldn't fight the narcos, because the United States was actually on the side of the traficantes. Does this sound counter-intuitive?...