Eight months after President Obama announced his decision to send 30,000 more troops to Afghanistan and to expand the counterinsurgency war there, we have seen enough—enough to know that the strategy cannot work, and enough to understand that the costs of continuing the war far outstrip any conceivable benefits.

This conclusion was more than buttressed by the WikiLeaks release of 92,000 classified military documents, which reveal that the Pentagon has repeatedly overestimated its ability to control events; that the Taliban have much broader support, including the active assistance of the Pakistani intelligence services, than has been portrayed; and that the Afghan army and police, whose training is the centerpiece of our eventual exit strategy, are even more distrusted by the Afghan people than has been reported. Virtually everything in the war logs confirms that this is a conflict we should not be waging.

After nearly nine years of war, it is clear that Afghanistan—with its complex regional and ethnic divisions, its long history of fierce resistance to occupying forces, its decentralized governance and tribal system, and its susceptibility to the interference of neighbors—does not lend itself to successful counterinsurgency.

In addition, a majority of Americans oppose the war, which is increasingly being questioned by politicians and pundits. As other presidents have learned, it’s not possible to wage a war that lacks public support and for which there is no clear measure of success. It is therefore time for the president to change policy; we cannot afford to wait for the policy review scheduled for December. The administration should take the advice of a majority of House Democrats and begin planning the "safe, orderly and expeditious redeployment" of US troops and start work on a regional diplomatic initiative to support reconciliation in Afghanistan.

As laid out by Obama last December, the administration’s strategy has two goals: one, to reverse the Taliban’s momentum in order to make them more pliant to negotiations at a time of Washington’s choosing. The other is to strengthen the capacity of the Afghan government so that it can hold, and eventually assume complete responsibility for, areas cleared by the surge of US and allied forces. These two objectives were to come together in the spring offensive in Marja and in a summer offensive in Kandahar, in the Pashtun heartland.

But, as the Pentagon admits, the offensive in Marja fell far short of the objectives. It revealed that even with overwhelming force, we cannot fully clear and hold territory with our own troops, let alone install a local government that can withstand Taliban intimidation.

Particularly problematic has been the performance of the Afghan government and security forces. Even if the Pentagon had been able to clear the area, transferring control to the Afghan security forces is a distant dream. Because of that, US commanders have indefinitely postponed the Kandahar offensive. The Obama administration may have softened its public criticism of President Karzai, but the Afghan government is a stew of corruption and opportunism, hardly able to deliver the most basic services. Meanwhile, the government seems more determined than ever to pursue its own agenda, which often conflicts with Washington’s. Standing up to the Americans may give Karzai a semblance of popular legitimacy he otherwise lacks, but it undercuts any partnership.

None of these factors can be easily changed by the newly appointed commander, Gen. David Petraeus. Trying to force Karzai to fall into line or exercising more direct control over the Afghan security forces would make the United States appear more like an occupier. And Petraeus’s proposal for building up village defense forces is fraught with problems, not the least of which is that it would empower local militias and warlords and add more fuel to the civil war.

In short, it simply is not in our power to produce the kind of Afghan government our strategy calls for. There are three reasons we should change course now.

§ Time is not on our side. Indeed, there is good evidence that we will be in an even more difficult position in six months or a year. The Pentagon presents counterinsurgency as a benign force to protect the population, but—as the WikiLeaks revelations about civilian casualties show—it is also deeply disruptive and destabilizing and can make reconciliation more difficult. Even if we are able to eliminate many Taliban leaders, younger and more radical ones may take their place. The US military has killed a large number of insurgent leaders, yet the Taliban have only grown stronger and more determined. Better to negotiate with the ones we know today than those who may be radicalized by the fighting to come.

§ The war is expensive—in money and lives and in the distraction it creates from other international and domestic goals. A drawdown of forces would allow Obama to stop the loss of American and Afghan lives, reduce the drain on the federal budget and redeploy resources to create jobs and rebuild the battered US economy. If there is no prospect of success, it is immoral to continue putting lives on the line and wasting money and resources that could create jobs and improve lives at home.

§ The uncertainty over whether the administration will adhere to the July 2011 drawdown—along with the steady stream of bad news from Afghanistan—has led to growing opposition in Congress, which is beginning to reflect public opinion. In June a majority of House Democrats supported legislation demanding an exit strategy and a timetable for withdrawal, and in late July the number of Democrats voting against supplemental funding for the war tripled, to more than 100—among them David Obey, chair of the House Appropriations Committee.

For these reasons, political and diplomatic progress over the next year will be difficult. It would be better, therefore, for the administration to clear the air with a firm timetable for withdrawal and redirect its efforts toward regional diplomacy than endure another year of infighting and backstabbing. This would change the "America as occupier of Muslim land" narrative to "America as regional peacemaker." As much as some may associate Afghanistan with the attacks of 9/11, the crisis there is now a regional one, not a national security threat that requires nearly 100,000 US troops and more than $100 billion a year. So it calls for a regional solution—one that needs American diplomacy, not American boots on the ground.

Afghanistan poses a key test of President Obama’s leadership, in part because it is one in which he must reverse course. But that change would offer immediate and long-term benefits to the nation if he acts with wise leadership now.