The strategic importance of these objectives is not in doubt. The question is whether they are attainable, and whether an increased troop commitment in Afghanistan will do much to advance them. The Islamabad government sincerely, even passionately, wants the United States and its allies to continue their Afghan campaign. But among Pakistan’s vast population, the West is much more unpopular  indeed, hated  than it was in 2006 or, for that matter, 2001. There is a danger that the surge will intensify that popular alienation, further fueling Islamic extremism and thus terrorism.

Little progress can be made toward regional stability without reducing tensions between Pakistan and India. India’s dalliance with the Afghan government, which has been given hundreds of millions of dollars in Indian aid, has increased the deep paranoia of the Pakistani Army and intelligence service. The status quo will only lead powerful elements of Pakistan’s security forces to continue to support Islamic militants as proxies against India.

Few responsible participants in the Afghan drama, even the most pessimistic, urge a precipitate withdrawal. We are too deeply committed for that. What seems important is to recognize that politics and diplomacy are the fundamentals, though they cannot progress unless security improves. Even the most limited stabilization program will founder unless all the regional powers, including Iran, become parties to it. It is difficult to imagine that the Karzai administration can raise its game sufficiently to gain a popular mandate strong enough to stop the Taliban.

President Obama said on Tuesday, “Unlike Vietnam, we are not facing a broad-based popular insurgency.” Yes, the Taliban command limited support, and have relatively few hard-core fighters. But many Afghans, especially Pashtuns, unite in dislike both for the Western “occupiers” and the Kabul regime.

Progress depends, as General McChrystal seems to recognize, on reaching accommodations with the tribes from the bottom up, not the top down. The smartest surge will be one of cash payments to local leaders. You can buy a lot of Afghans for a small fraction of the cost of deploying a Marine company.

Perhaps the greatest problem for Western policymakers is that Taliban leaders watch CNN and Al Jazeera. They know that the British public has turned against the war, probably irrevocably, and that American opinion is deeply divided. They believe they have more patience than us, and they may be right.

The president’s troop surge was perhaps politically inescapable. But any chance of salvaging a minimally acceptable outcome hinges not on what American and allied soldiers can do on the battlefield, but on putting together a coherent political strategy. Mr. Obama’s speech represented a gesture to his generals rather than a convincing path to success in Afghanistan.