Last year I wrote about how in the diligent and otherwise orderly policy review on Afghanistan that President Obama conducted in the latter half of 2009, the principal point of disorderliness was the insistence by the Department of Defense and the military that there was only one right way to fight the war and thus only one right level of U.S. troops. The president reportedly had to struggle to get more than one option out of the Secretary of Defense and the military and eventually had to construct his own compromise that gave the military something less than what it had insisted on. I noted that the Defense Department's posture was a classic example of standing Clausewitz on his head and making the scope and objective of a war fit military requirements rather than making the military the servant of a politically determined objective.

With an impending presidential decision on how much of a troop withdrawal to begin next month, the same dynamic appears to be at work again. Secretary of Defense Robert Gates, notwithstanding his imminent retirement, has been vocal in arguing for as small a withdrawal as possible, with the uniformed military contributing arguments in the same direction. Expect to hear again, as we heard in the earlier policy review, talk on Capitol Hill and elsewhere about how the military knows best about what it takes to accomplish a wartime mission and how therefore much deference ought to be accorded to the military's views.

The military does indeed know that best, and our senior military officers are honorable leaders who do their best to determine the requirements for carrying out what they understand to be their mission, which in this case involves trying to stabilize Afghanistan through a counterinsurgency. But that is not the question before the president. The question has less to do with identifying means to accomplish a given end in Afghanistan than with identifying what the end ought to be. The question involves determining how much can be accomplished at what cost, how much the accomplishment contributes to the national interest, and whether the whole trade-off is in the national interest. The question goes well beyond the military's purview.

One also continues to hear debate about policy toward Afghanistan phrased in dichotomous terms: that such-and-such is at stake and we need to stay the course to achieve that stake rather than fail to achieve it. But that, too, is not really the sort of question before the president. It is more a matter of degree. It is a matter of what amount of additional cost and effort will yield what amount (if any) of benefit, over and above what we would be seeing anyway.

The original reason and still the main rationale of the war involves terrorism. But even before the demise of Osama bin Laden, there were ample reasons to conclude that the ratio of war costs to any increase in Americans' safety from terrorism is unattractively large (and that there might be no increase at all). The reasons have to do with such things as al-Qaeda barely being in Afghanistan, the Afghan Taliban not being an international terrorist group, territorial control in Afghanistan not being one of the more important factors in determining what threat a terrorist group may pose, and the impossibility of even a sustained counterinsurgency securing all the territory in Afghanistan anyway.

Rationales for the war these days often invoke Pakistan and the stakes the United States has there. But events in Pakistan will shape Pakistan's future far more than events in Afghanistan, where the Pakistanis we are supposedly trying to shore up are still doing business with the Afghan Taliban we are fighting. And in another confusion of ends and means, U.S. dependence on Pakistan as a supply route for the war effort in Afghanistan reduces U.S. leverage on Pakistan to do anything else.

Then there are issues of what kind of Afghan society the United States is to leave behind, and a responsibility not to consign Afghans to barbarism. Here it is especially important to remember that we are dealing with degrees and not absolutes. As disagreeable as the Afghan Taliban are, much of what we may find alien and even repugnant in Afghanistan is not just a matter of the Taliban. A recent reminder of this is a declaration by the country's Council of Religious Scholars, which meets regularly with President Hamid Zarzai to advise him on religious matters, calling for the closing of independent media outlets on grounds of “immorality” (which means such things as coverage of the radicalizing influence of madrassas, or anything having to do with women's rights).

Americans owe gratitude to their senior military leaders, as to the troops who serve under them, for doing their best to prosecute a difficult war. Let us not add to their burden by looking to them to decide matters that are the responsibility of political leaders.