In searching and scratching for a reason for continuing the presence of U.S. troops in Afghanistan beyond 2014, after thirteen years of warfare, the most commonly stated rationales come up short. The original purpose of the military intervention involved, of course, responding to an attack by a terrorist group that at the time had a presence in Afghanistan. But what is left of that group has not been based in Afghanistan for a long time. There also are still the questions of how much Afghanistan is to be considered unique as a potential base for terrorist attacks, and how much any physical base in a faraway place affects the level of terrorist threat to the United States. Other rationales involving human rights or democracy in Afghanistan run up against questions both about how much any U.S. military effort in Afghanistan can accomplish on those fronts and about the priority such objectives have or ought to have among U.S. interests.

Those inside and outside the administration who have thought hardest about what is and is not being accomplished by a U.S. military presence in Afghanistan keep coming back to a different reason: that we need that presence to provide enough security to operate unmanned aerial vehicles from Afghanistan (and perhaps to do enough for other aspects of Afghan security so that the government of Afghanistan will permit the continued operation of the drones from Afghan soil), and we need the drones to keep whacking at terrorists next door in Pakistan. David Sanger and Eric Schmitt's article on this subject in the New York Times is on the mark regarding the thinking on this subject. There are two undeniable facts involved in this particular rationale for staying in Afghanistan. One is that a base in Afghanistan affords a geographic advantage given where many of the targets are located. The second is that missiles fired from drones have eliminated a significant number of malevolent individuals in northwest Pakistan.

Think even harder and more broadly, however, and this rationale for a continued military presence in Afghanistan exhibits several patterns of thought that in most other circumstances would be considered fallacious.

One is to confuse availability of use with desirability of use. The drone strikes often have been considered “the only game in town” in terms of getting at undesirables in the wilds of Waziristan. But this in effect means that because the tool we happen to have is a hammer (and a very nifty hammer at that), not only do things start looking like nails, but we also feel an uncontrollable urge to keep pounding, whether or not pounding is apt to do us more good than harm.

Another pattern is to confuse ends and means. We are not using a particular lethal tool to, say, provide security and stability in a country. We are trying to provide enough security and stability in a country to be able to use the tool. There was some similar ends/means confusion earlier in the war in discussion about the role of NATO. An alliance is normally considered to be an instrument for doing something such as fighting a war, but some of the discussion was about how the war ought to be fought to maintain the health of the alliance.

A further fallacious tendency is to give disproportionate emphasis to what is visible and immediate, whether or not it is really more important than what is longer term and more obscured. This involves the pros and cons of the drone strikes themselves. It is easy to chalk up as an accomplishment the physical elimination of a suspected terrorist, because it is visible and immediate. It is a different question whether when all the more distant and less quantifiable effects such as popular reactions are taken into account, the net benefit is positive even just from a counterterrorist point of view.

Finally, there is a disproportionate focus on a tree rather than the forest. Extending an entire overseas military expedition for the sake of being able to use one weapon system in one particular area is an extraordinary deference to the tree while losing sight of the forest. Drones flown from a runway in Afghanistan are just one tool used in one location on behalf of one objective out of the many that ought to bear on U.S. foreign policy decisions.

Publicly stated rationales for foreign wars often diverge at least partly from the real reasons in the minds of policy-makers. But thinking about public reactions can be a useful check on the direction of non-public thinking and whether it is exhibiting too much of the sorts of fallacies mentioned above. How would the American public react if the president and Congress clearly explained that the reason America's longest war might be made even longer is that Afghanistan is a convenient location for operating unmanned aerial vehicles?