Chris Preble's piece about fragile and reversible gains provides excellent insight into a frequently heard theme in discourse concerning military expeditions overseas, and into how arguments to extend those expeditions often stray from a sober consideration of the costs and benefits of doing so. The yearning to go beyond minimal accomplishment of military objectives and to try to achieve something grander and more lasting is partly rooted in universal human psychology, such as the disinclination to treat sunk costs as truly sunk. Preble even refers to Pericles as having voiced one of the themes in question. The tendency to keep stretching for absolute, irreversible victories is, however, disproportionately American. The tendency is more pronounced among Americans than among others for reasons related to the unique circumstances and history of the United States.

Living in a peculiarly powerful and successful republic makes it easier to believe that the nation really can achieve absolute, irreversible victories. Sure, the United States has had failures, including some really big ones such as the Vietnam War. But even that costly failure, given the passage of time and of generations and the attitudinal balm of a splendid victory such as Operation Desert Storm—the reversal in 1991 of the Iraqi seizure of Kuwait—has not prevented restoration of hubristic optimism about what the United States can use its power to accomplish. One of the reactions to Desert Storm—specifically, the neoconservative reaction—featured once again the idea that accomplishment of a limited military aim is not enough and that the United States should go for the gold. Reversing Saddam Hussein's aggression was not enough to sate the neocons' hunger for something grander in the Middle East, involving the elimination of Saddam altogether. And that hunger, coupled with an arrogant belief in the ability to accomplish a big irreversible victory, led to another costly military misadventure a decade later.

Another aspect of America's involvement with the world that has shaped the attitude Preble has described has been an episodic history in which the United States from time to time has sallied forth to vanquish the foreign menace du jour, and between sallies has retired behind its ocean moats to enjoy normalcy. The idea that the sallies should accomplish something lasting and preferably irreversible flows naturally from the whole vanquish-then-relax concept of using military force to deal with foreign threats. The same frame of mind does not get found in lesser countries around the world, where foreign threats must be handled through continuous management rather than episodic efforts.

The policy elites who write about fragile, reversible gains in places such as Iraq or Afghanistan do not necessarily anticipate a period of relaxation. In fact, the agenda of some of them may include an unending military presence in such places, including permanent bases. But the American mindset to which their words appeal is one that believes with just a little more effort, we can get over the last hump of whatever campaign we are waging, get rid of once and for all whatever problem or threat we are confronting, and go home a winner.

The mindset shapes American attitudes and responses on many different problems. When Secretary of Defense Leon Panetta recently declared that the United States was “within reach of strategically defeating Al Qaeda,” his comment got attention partly because it appealed to the same mindset. Mr. Panetta himself is not part of that mindset, and his remark, made during a visit to Afghanistan, probably was intended partly as support for his president's troop withdrawal decisions. Most of Mr. Panetta's predecessors are not part of the mindset either; Donald Rumsfeld correctly reminded us that besting international terrorism will not involve a surrender on the deck of the USS Missouri. But for many in the American public—which already oversimplifies the topic by equating terrorism with Al Qaeda—such a remark raises the hope that with a little more effort, we can do away with the threat altogether. This perception was further encouraged by Secretary Panetta's elaboration that the United States is now focusing on 10 to 20 key leaders of Al Qaeda. Hearing this, it is easy for Americans to believe that if we can just get those last 10 or 20 bad guys, the terrorist threat will be wiped out, just as smallpox or rinderpest was wiped out when the last few cases were found and dealt with.

Being a superpower with a history as exceptional as that of the United States means carrying certain burdens. The purveyors of the “we have to stay the course so that fragile gains will not be reversed” concept see one of those burdens as, well, staying the course in things such as foreign wars. A less commonly understood burden is having the cognitive limitation that leads many Americans to believe mistakenly that staying a course really can achieve irreversibility.