A continuous and repetitive thread in the commentary on the decade since 9/11—one might almost call it an endless and open-ended theme—was the plaintive observation that the struggle against al-Qaida and its surrogates is somehow a “war without end.” (This is variously rendered as “perpetual war” or “endless war,” just as anti-war articles about the commitment to Iraq used to relentlessly stress the idea that there was “no end in sight.”)

I find it rather hard to see the force of this objection, or indeed this description. Was there ever a time when we involved ourselves in combat, or found ourselves involved, with any certain advance knowledge about the timeline and duration of hostilities? Are there two kinds of war, one of them term-limited? A bit like that other tempting but misleading separation of categories—between “wars of choice” and “wars of necessity”—this proves upon closer scrutiny to be a distinction without much difference.

In order even to aspire to such a nebulous timeline, there would first have to be consensus on when the war actually started. For example, I would say that hostilities between the United States and Saddam Hussein began in the early 1990s, if only at a relatively low level, after he had violated all the conditions of the cease-fire that had allowed him to retain power in 1991, and after he had begun regularly firing upon the planes that patrolled and enforced the cease-fire and the “no-fly” zones. For more than a decade, the only response to this was more air patrols and a reliance on a crumbling regime of sanctions. That really wasa case of “no end in sight.” But something tells me that this is not the sort of example that my opponents have in mind.

Then again, one might ask how long we have been at war with al-Qaida or its equivalents. Since the attack on the World Trade Center in 1993? Since the destruction of the U.S. embassies in Africa? Since the near-sinking of the USS Cole in Aden harbor in 2000? Even to invite these questions is to arouse the unnerving suspicion that there was quite a long period during which al-Qaida was at war with us, but we did not understand that we were at war with it. It was precisely that queasy feeling that was beginning to creep over some of us a while before the events of a decade ago dispelled most doubts. And it would have been just as true to say “no end in sight” on Sept. 12, 2001, as it would be to say it today—more true, if anything. So once again, those who want to set the clock must be crystal clear about when they think the confrontation started running.

Attitudes toward length are often a good clue to attitudes toward outcome. During the Bosnian conflict, those of us who favored using force to lift the siege of Sarajevo were accused of advocating a tactic that would “lengthen” the war. Even in the trivial sense of being true by definition (anything that denied Gen. Ratko Mladic a cheap, easy, and swift victory over civilians was necessarily war-prolonging to some extent), this wasn’t true in any serious way. The relatively brief bombardment of Serbian artillery positions had the effect of exposing the hollowness of Mladic’s military strength: Within an amazingly short time, Slobodan Milosevic himself was at Dayton asking for terms. One might phrase it like this: Intervention slightly lengthened hostilities in the short term, but drastically shortened them in the long term. (Milosevic later misinterpreted the Dayton agreements as lenience and tried to repeat his Bosnian tactics in Kosovo. But even if this could be construed as war-prolonging, it also led to the eventual defeat of his army and overthrow of his regime, and thus to a conclusive finish.)

Arguments about duration are often of great historical significance, going far beyond the battles of mere hindsight. For instance, the conventional wisdom among historians holds that United States military intervention in Europe in 1917 had the salutary effect of persuading the German high command that, with another fresh and well-equipped force deployed against it, it could not hope to prevail against the British and French alliance. But another explanation of the same events shows the war on the Western Front actually being prolonged. Before President Woodrow Wilson abandoned neutrality and committed American forces in strength, the Germans had been fighting with exceptional success. Their prowess had led to calls, especially in London, for a negotiated peace. But the arrival of a new ally dissipated all such talk and compelled the Germans to fight until the bitter end. Not only that, but when peace terms were finally discussed, the French were allowed and enabled to press their most vindictive economic and territorial claims against Germany. That the Versailles Treaty led to the rise of Nazism and thus to the “Second” World War, or rather Part 2 of the first one, is a conclusion that few historians now dispute. So short-war advocates should know to beware of what they ask for.

A final objection to the dogma of brief engagements is more commonsensical. On the whole, perhaps it is best not to tell your opponent in advance of the date when you plan to withdraw your forces. Many American generals, we understand, were critical of the president’s original decision to announce a deadline for the endgame in Afghanistan. Certainly, there seem to be upsetting signs of Afghan national army units, in particular, basing their calculations on who can be counted on to be still present as the months go by. Difficult to blame people for consulting their own self-interest in this blunt way.

Human history seems to register many more years of conflict than of tranquillity. In one sense, then, it is fatuous to whine that war is endless. We do have certain permanent enemies—the totalitarian state; the nihilist/terrorist cell—with which “peace” is neither possible nor desirable. Acknowledging this, and preparing for it, might give us some advantages in a war that seems destined to last as long as civilization is willing to defend itself.