Editor’s note: Garrison Keillor is taking a break from his weekly column so that he can finish a screenplay and start writing a novel. His syndicate tells the Tribune he intends to return but could not give a time. Meanwhile, we offer American Voices, a collection of columnists.

As Gen. David Petraeus assumed his new command in Afghanistan this week, he took up a strategy that has already failed — though not for the reasons most people assume.

Certainly, as most everyone knows, the battle plan appears hopeless. Every night in Marja, Taliban killers post “night letters” in mosques and other public places, warning city residents they will be killed if they cooperate with the Americans. The next day, quite often, they follow through on their threats.

American and NATO troops “liberated” Marja in February, hoping it would become a showplace, and now occupation forces number one for every eight city residents. Still, more people are dying in gun battles on the city’s streets right now than during the operation in February. Local officials are afraid to travel by car to the provincial capital, Lashkar Gah. They take a helicopter instead, even when the drive would take only 20 minutes.

Before he was fired last month, Gen. Stanley McChrystal called Marja a “bleeding ulcer.” All of that is part of a noxious stew of problems on the battlefield. Still, in 2005 and 2006, the war in Iraq looked equally hopeless. Since then, however, the situation there has improved significantly.

But a larger problem afflicts the effort in Afghanistan, one that coalition forces are virtually powerless to address. That is the population’s blighted state of affairs. Consider a few statistics that limn the people’s lives.

At least 26 of every 100 children born in Afghanistan die before they reach the age of 5. UNICEF says that’s the worst child-mortality rate in the world. Of those who survive, almost 60 percent suffer from moderate to severe stunting — also the world’s highest rate. Stunting results from sickness or malnutrition during infancy, and it’s irreversible. The children grow up to be small and not very smart.

It makes sense, then, that fewer than one-third of Afghan adults can read and write. On average, they earn about $250 a year and die before they reach age 45 — also among the lowest figures in the world. Finally, they are served by a government that is practically the most corrupt on the planet. Transparency International rates only one country, Somalia, as worse.

The cornerstone of the coalition’s counterinsurgency strategy calls for the Afghan government to step up and provide stronger government institutions and public services. Afghans must begin to regard President Hamid Karzai’s administration as an efficient, helpful alternative to the Taliban. The government must also provide security nationwide once the Americans leave.

But consider what the dark social statistics mean for that plan. An estimated 90 percent of the new recruits for the Afghan army are illiterate. You don’t have to read to shoot a rifle, but you do need to be able to read the rifle’s instruction manual.

The Afghan police are no better educated, but that’s not the most serious problem. Across the country, police set up impromptu checkpoints along the road. They stop cars and demand a payment for permission to pass. These are the lawmen who are going to protect the people after the Americans leave? As it is, most won’t investigate a crime unless the victim pays a bribe.

What is the Afghan government doing to remedy these pernicious problems? It is sending suitcases full of cash, at least $1 billion a year in bribe proceeds and purloined foreign aid, out of the country to private accounts in Dubai or other banking capitals. That’s not a secret; the shipments are declared as they pass through Kabul’s airport. The money has been laundered through hawalas, private money-transfer businesses, and the government gives this practice its blessing.

“Taking money out of the country is fine,” Karzai said during a news conference last month. “The relatives of government officials can do this,” even “my brothers,” who are generally regarded as the nation’s most avaricious thieves.

More money leaves the country for private bank accounts each year than the government collects in taxes and fees, the Wall Street Journal reported. When pressed, Karzai did allow that “there’s a possibility of corruption.” The U.S. is well aware of the problem. Congress is demanding investigations, the military is chartering audits and inquiries.

But that leaves the United States in an impossible position. To win the war in Afghanistan, the U.S. must turn a nation that stands as a model for bald-faced thievery into a clean, honest institution that cares for its people, now the most neglected in the world.

It can’t be done.

Joel Brinkley, a professor of journalism at Stanford University, is a former foreign correspondent for the New York Times.