A number of commentators have remarked of late on the ominous parallels between the situation in Afghanistan today and the quagmire in Vietnam in the 1960s.

The United States is allied with a corrupt local government that rigs the political process and has little legitimacy in the eyes of its own people. Check.

The United States seeks to hand over more counterinsurgency work to local police and military forces, but they are ill-trained and poorly motivated. Check.

Villages that seem to be friendly one day turn out to be hotbeds of insurgent activity the next, and U.S. soldiers on patrol are never sure who their friends are. Check.

Because the insurgents melt into the civilian population, attempts to target them inevitably end up killing civilians, earning Washington more enemies. Check.

The U.S. military admits all isn't going according to plan, but says it can win if it's given more troops. Check.

U.S. public support for the war has dropped, with most Americans now opposed to it. Check.

Many of the skeptics point out that the British and Soviets tried to conquer Afghanistan and failed. The high priests of counterinsurgency, while admitting that the country's mountainous terrain and long tradition of independence pose challenges, nonetheless claim that the United States will triumph where the British and Soviets did not.

All that's needed, they say, are more troops so that fence-sitting villagers who want to support the U.S. occupation will feel safe doing so, and lots of development projects so that the average Afghan will see his or her life improve under occupation.

If only we build enough schools, clinics and bridges, so the argument goes, Afghans will ask themselves the question Ronald Reagan famously posed to the American people — "Are you better off now than you were four years ago?" — and they will reject the Taliban.

This all may sound good in the airtight world of White House briefings, but, in the real world, the very phenomena the counterinsurgency gurus see leading to success — more troops and more development — will make the U.S. effort fail. Counterinsurgency in Afghanistan contains within itself the seeds of its own ineluctable failure.

This is so for three reasons. The first is Newton's Third Law, the second is the development dilemma and the third is the prohibitionist paradox.

To begin with Newton's Third Law, readers who paid attention in high school will recall it states that for every action there is an equal and opposite reaction. This applies to counterinsurgency as well as physics.

Putting more U.S. troops into Afghanistan will make it possible to capture and kill more Taliban, and it will provide reassurance to some fence-sitting peasants that the United States means business.

However, more U.S. troops in Afghanistan also means that more homes will be rudely searched in the middle of the night, more Afghan women will be dishonored — deliberately or inadvertently — in contacts with U.S. soldiers, and more U.S. soldiers will intrude into Afghan daily life with their alien clothes, speech and body language.

The Pentagon will try to minimize the insult through cultural sensitivity training and new doctrines that emphasize befriending the locals, but they will fail because it's in the very nature of counterinsurgency that occupying forces must be intrusive to be effective. And when you have thousands of foreign troops being shot at, accidents and atrocities happen. The more such troops you have, the more accidents and atrocities you get.

This is exactly the point made recently to New York Times columnist Nicholas Kristof by an anonymous group of former intelligence officials: "Our policy makers do not understand that the very presence of our forces in the Pashtun areas is the problem. The more troops we put in, the greater the opposition. We do not mitigate the opposition by increasing troop levels, but rather we increase the opposition and prove to the Pashtuns that the Taliban are correct."

Some are now suggesting this problem can be solved by building up Afghanistan's own military and police forces and relying less on U.S. troops. But Pashtuns don't like being policed by Tajiks and Uzbeks much more than they like U.S. soldiers in their villages.

The second problem for the Obama Administration's new counterinsurgency doctrine is what I call the development dilemma.

To begin with, development projects make foreigners and their values more visible and thus inflame some local cultural opposition. More importantly, every time the United States increases its development budget in Afghanistan, it also increases the Taliban's budget.

This is because a major source of Taliban funding consists of taxes it levies on Western development projects. The more schools, bridges and clinics Washington builds, the more money the Taliban will have to blow them up and to attack U.S. soldiers.

This dynamic is illuminated in a fascinating article by Jean MacKenzie, writing for GlobalPost. MacKenzie tells her readers about "the manager of an Afghan firm with lucrative construction contracts with the U.S. government" who has to negotiate not only with development bureaucrats but also with the Taliban contracts officer.

He "builds in a minimum of 20% for the Taliban in his cost estimates. The manager, who will not speak openly, has told friends privately that he makes in the neighborhood of $1 million per month. Out of this, $200,000 is siphoned off for the insurgents."

She mentioned another Afghan contractor who told her, "I was building a bridge. . . . The local Taliban commander called and said, 'Don't build a bridge there, we'll have to blow it up.' I asked him to let me finish the bridge, collect the money — then they could blow it up whenever they wanted. We agreed, and I completed my project."

This is no way to win a war.

Finally, there is the prohibitionist paradox. According to the Associated Press, Afghanistan supplies 93% of the world's opium.

Taxes levied on the opium trade are a major source of revenues for the Taliban. Thus, the United States has two reasons to eradicate opium cultivation in Afghanistan: It will cut off a source of revenue for the Taliban, and it will reduce the flow of one of the deadliest drugs in the world, heroin, to the United States and Europe.

However, Afghan citizens don't feel the same way about opium as, say, Drug Enforcement Agency (DEA) agents do. By some estimates, opium accounts for almost one-half of Afghanistan's gross domestic product, and opium is so deeply entrenched in Afghan life that it functions as a sort of reserve currency: Children buy candy with it, mothers buy food with it, men pay barbers with it.

If the United States attacks the opium trade, which it has now decided to do, it might as well open recruiting stations for the Taliban. But if it leaves the opium trade alone, it will be assuring the Taliban a steady source of revenue. Lose-lose.

The White House is speaking of victory in Afghanistan, debating the metrics by which it will be measured. This is surreal. Unless defeat is redefined as triumph, victory isn't possible.

The war in Afghanistan is like the war on drugs. It can be fought endlessly, but it cannot be won. The only question is how many Americans and Afghans will die, and for how long, before we concede defeat.

Say our job is done now, Mr. President, and leave.

**Editor’s Note: This feature first appeared on September 21, 2009, in the Bulletin of the Atomic Scientists, which can be viewed here.