At periodic intervals, the American body politic has shown a marked susceptibility to messianic fevers. Whenever an especially acute attack occurs, a sort of delirium ensues, manifesting itself in delusions of grandeur and demented behavior.

By the time the condition passes and a semblance of health is restored, recollection of what occurred during the interval of illness tends to be hazy. What happened? How’d we get here? Most Americans prefer not to dwell on the questions. Feeling much better now! Thanks!

Gripped by such a fever in 1898, Americans evinced an irrepressible impulse to liberate oppressed Cubans. By the time they’d returned to their senses, having acquired various parcels of real estate between Puerto Rico and the Philippines, no one could quite explain what had happened or why.

In 1917, the fever suddenly returned. Amid wild ravings about waging a war to end war, Americans lurched off to France. This time the affliction passed quickly, although the course of treatment proved painful: confinement to the charnel house of the Western Front, followed by bitter medicine administered at Versailles.

The 1960s brought another bout (and yet more disappointment). An overwhelming urge to pay any price, bear any burden landed Americans in Vietnam. The fall of Saigon in 1975 seemed, for a brief interval, to inoculate the body politic against any further recurrence. Yet the salutary effects of this “Vietnam syndrome” proved fleeting. By the time the Cold War ended, Americans were running another temperature, their self-regard reaching impressive new heights.

Then came 9/11, and the fever simply soared off the charts. The messiah nation was really [filtered word] and was going to fix things once and for all.

Nearly 10 years have passed since Washington set out to redeem the greater Middle East. The crusades have not gone especially well. In fact, in the pursuit of its mission, the American messiah has pretty much worn itself out.

Today, the post-9/11 fever finally shows signs of abating, though the sickness has by no means passed. Oddly, it lingers most strongly in the Obama White House, where a keenness to express American ideals by dropping bombs persists.

Yet, despite the urges of some in the Obama administration, after nearly a decade of self-destructive flailing about, American recovery has become a distinct possibility. Here’s some of the evidence:

In Washington, it’s no longer considered a sin to question American omnipotence. Take the case of Robert Gates. The outgoing secretary of Defense certainly restored a modicum of competence and accountability to the Pentagon. But the most enduring Gates legacy is likely to be found in his willingness, however belated, to acknowledge the limits of American power.

No one can charge Gates with being an isolationist or a national security wimp. So when he says anyone proposing another major land war in the Middle East “should have his head examined” — citing the authority of Douglas MacArthur, no less — people take notice. Or more recently there is this. “I’ve got a military that’s exhausted,” Gates remarked. “Let’s just finish the wars we’re in and keep focused on that instead of signing up for other wars of choice.” Someone should etch that into outer walls of the Pentagon’s E-ring.

Half a dozen years ago, “wars of choice” were all the rage in Washington. No more. Thank you, Mr. Secretary.

Or consider the officer corps. There is no “military mind,” but there are plenty of minds in the military, and some numbers of them are rethinking the role of military power.

Consider, for example, “Mr. Y,” author of “A National Strategic Narrative,” published this spring to considerable acclaim by the Woodrow Wilson International Center for Scholars. The actual authors of this report are two military professionals, one a Navy captain, the other a Marine colonel.

What you won’t find in this document are jingoist chest-thumping and calls for a bigger military budget. If there’s an overarching theme, it’s pragmatism. Rather than the United States imposing its will on the world, the authors want more attention paid to investment at home.

The world is too big and complicated for any one nation to call the shots, they insist. The effort to do so is self-defeating. “As Americans,” Mr. Y writes, “we needn’t seek the world’s friendship or proselytize the virtues of our society. Neither do we seek to bully, intimidate, cajole or persuade others to accept our unique values or to share our national objectives. Rather, we will let others draw their own conclusions based upon our actions.... We will pursue our national interests and let others pursue theirs.”

And finally, by gum, there is the U.S. Congress. Just when that body appeared to have entered a permanent vegetative state, a flickering of intelligent life has made its reappearance, and Democrats and Republicans alike — albeit for different reasons — are raising serious questions about the nation’s propensity for multiple, open-ended wars.

Some members cite concerns for the Constitution and the abuse of executive power. Others worry about the price tag. With Osama bin Laden out of the picture, still others insist that it’s time to rethink strategic priorities. No doubt partisan calculation or personal ambition figure alongside matters of principle. After all, they are politicians.

Given what polls indicate is a growing public unhappiness over the Afghanistan war, speaking out against the war these days doesn’t exactly require political courage. Still, the possibility of our legislators reasserting a role in deciding whether or not a war actually serves the national interest, rather than simply rubber-stamping appropriations and slinking away, now presents itself. God bless the United States Congress.

Of course, at the first signs of self-restraint, you can always count on the likes of Sen. John McCain or the editorial board of the Wall Street Journal to decry (in McCain’s words) an “isolationist-withdrawal-lack-of-knowledge-of-history attitude.” In such quarters, fever is a permanent condition, and it’s always 104 and rising. Yet it is a measure of how quickly things are changing that McCain himself, once deemed a source of straight talk, now comes across as a mere crank.

In this way, nearly a decade after our most recent descent into madness, does the possibility of recovery finally beckon.

• Bacevich is professor of history and international relations at Boston University.