In Afghanistan today, the United States and its allies are using the wrong means to vigorously pursue the wrong mission. Persisting on the present course as both John McCain and Barack Obama have promised to do will turn Operation Enduring Freedom into Operation Enduring Obligation. Afghanistan will become a sinkhole consuming resources neither the U.S. military nor the U.S. government can afford to waste.

The allied campaign in Afghanistan is now entering its eighth year. The operation was launched with expectations of a quick, decisive victory but has failed to accomplish that objective. Granted, the diversion of resources to the misguided war in Iraq has forced commanders in Afghanistan to make do with less. Yet that doesn't explain the lack of progress. The real problem is that Washington has misunderstood the nature of the challengeAfghanistan poses and misread America's interests there.

One of history's enduring lessons is that Afghans don't appreciate it when outsiders tell them how to govern their affairs--just ask the British or the Soviets. U.S. success in overthrowing the Taliban seemed to suggest this lesson no longer applied, at least to Americans. That quickly proved an illusion.

In Iraq, toppling the old order was easy. Installing a new one to take its place has turned out to be infinitely harder.

Yet the challenges of pacifying Afghanistan dwarf those posed by Iraq. Afghanistan is a much bigger country--nearly the size of Texas--and has a larger population that's just as fractious. Moreover, unlike Iraq, Afghanistan possesses almost none of the prerequisites of modernity; its literacy rate, for example, is 28 percent, barely a third of Iraq's. In terms of effectiveness and legitimacy, the government in Kabul lags well behind Baghdad not exactly a lofty standard. Apart from opium, Afghans produce almost nothing the world wants. While liberating Iraq may have seriously reduced the reservoir of U.S. power, fixing Afghanistan would drain it altogether.

Meanwhile, the chief effect of allied military operations there so far has been not to defeat the radical Islamists but to push them across the Pakistani border. As a result, efforts to stabilize Afghanistan are contributing to the destabilization of Pakistan, with potentially devastating implications. September's bombing of the Marriott hotel in Islamabad suggests that the extremists are growing emboldened. Today and for the foreseeable future, no country poses a greater potential threat to U.S. national security than does Pakistan. To risk the stability of that nuclear-armed state in the vain hope of salvaging Afghanistan would be a terrible mistake.

All this means that the proper U.S. priority for Afghanistan should be not to try harder but to change course. The war in Afghanistan (like the Iraq War) won't be won militarily. It can be settled--however imperfectly--only through politics.

The new U.S. president needs to realize that America's real political objective in Afghanistan is actually quite modest: to ensure that terrorist groups like Al Qaeda can't use it as a safe haven for launching attacks against the West. Accomplishing that won't require creating a modern, cohesive nation-state. U.S. officials tend to assume that power in Afghanistan ought to be exercised from Kabul. Yet the real influence in Afghanistan has traditionally rested with tribal leaders and warlords. Rather than challenge that tradition, Washington should work with it. Offered the right incentives, warlords can accomplish U.S. objectives more effectively and more cheaply than Western combat battalions. The basis of U.S. strategy in Afghanistan should therefore become decentralization and outsourcing, offering cash and other emoluments to local leaders who will collaborate with the United States in excluding terrorists from their territory.

This doesn't mean Washington should blindly trust that warlords will become America's loyal partners. U.S. intelligence agencies should continue to watch Afghanistan closely, and the Pentagon should crush any jihadist activities that local powers fail to stop themselves. As with the Israelis in Gaza, periodic airstrikes may well be required to pre-empt brewing plots before they mature.

Were U.S. resources unlimited and U.S. interests in Afghanistan more important, upping the ante with additional combat forces might make sense. But U.S. power--especially military power--is quite limited these days, and U.S. priorities lie elsewhere.

Rather than committing more troops, therefore, the new president should withdraw them while devising a more realistic--and more affordable--strategy for Afghanistan.

Bacevich is professor of history and international relations at Boston University, and the author, most recently, of "The Limits of Power: The End of American Exceptionalism." 
Originally posted at Newsweek. 
© 2008