UQ AL-TALH, Yemen — Want to buy a submachine gun?

This little market town in the wild, wild north of Yemen has more than 50 shops selling all kinds of toys for boys. A used Uzi goes for $170, a machine pistol with silencer is $350, and a brand-new AK-47 assault rifle goes for nearly $400.

Grenades are $4 each. An antitank mine is $22. A rocket-propelled grenade launcher is $500. An arms merchant I met here might even be able to find you an antiaircraft gun or a tank. No sales tax.

This is Yemen, where we're preparing to send American soldiers to open a new front in the war on terrorism. I admire the instinct of trying to boost security here, but the bottom line is that we're going to send our troops on a poorly defined mission into a country where they're not wanted, where grenades cost $4 each.

The plan is for the Americans to train Yemeni troops. But the Yemen government's main problem in controlling terrorism is not that soldiers are poorly trained. Instead it is that for reasons of history, culture and tribal politics, the central government doesn't entirely control the hinterlands.

Americans who gripe about big government and high taxes, who believe the state that governs best governs least, would love Yemen. The central government controls the beautiful old capital, Sana, and a chunk of turf to its south and west. Beyond that is a delicate balancing act with local sheiks.

When I wanted to come up here into northern Yemen, I took an escort from the government including, for one stretch of road, a pickup truck loaded with seven soldiers and a heavy machine gun mounted in back. But more important, to avoid kidnapping (Yemen's favorite sport) it was prudent to get invitations from the leading sheiks.

"No one will pay attention to the government escort," a wise Yemeni explained to me. "But if you're invited by the sheiks, they won't dare bother you. They'll be afraid of retaliation from the sheiks."

The frailty of the government's authority was underscored on the road north, when we were stopped at a roadblock by a group of men with assault rifles. It was Yemeni code: a stick across the road means you stop, or you get your tires shot out.

It turned out that one of the men at the roadblock was owed money by a man of another tribe. So they were stopping all traffic to look for a car driven by any member of that other tribe: they planned to confiscate the car and keep it until the money was repaid. There were no police or army units to keep the road open, and the roadblock would remain until either the tribesmen got their car or the debt was paid.

Vice President Dick Cheney dropped in on Yemen last week, for a useful show of support — even if it was also a show of nervousness, for Mr. Cheney spent only two hours in the country, and he switched to a military plane that took evasive maneuvers as it landed. Opposition parties, eager to profit politically, said in a statement that the visit would "lead to more bloodshed."

American spooks worry that Yemen might provide a new base for terrorists like Osama bin Laden (who in a 1996 interview praised Yemen, his ancestral home, as a place in which he might settle). That's the reason for trying to bolster the government by training its army. It's a worthy goal, and if the training were conducted in the United States or in another country like Saudi Arabia it would not risk undermining the government's moral authority.

So why not conduct the same training, the same technology transfers, outside of Yemen?

By the way, a parting thought:

A couple of weeks ago I wrote about firearms, and I noted that England and Japan — which tightly regulate handguns — have much lower gun death rates than the United States. I got a barrage of e-mail. Much of it was thoughtful and well-reasoned criticism, but there were also plenty of blasts urging me to move to Japan or England.

Thanks for the advice. And if you're so bothered by gun registration, and so convinced that guns don't kill people, then consider moving to a nice mud-brick home here in Suq al-Talh. With you and everybody else carrying around an assault rifle, with armor-piercing rounds in your bandolier, with a couple of grenades in your pockets, you'll really feel safe. You'll love the freedom!