Midway through his inaugural address, Barack Obama proclaimed, "A decade of war is now ending." A cynical listener might respond: "And a new decade of war is about to begin." Obama sounded pacific notes Monday. But it will be a huge surprise if he can get through four years without going to war.

Military force should not be a frequent recourse for our leaders. For the first century or so of the republic, it wasn't. Leaving aside the intermittent war against the Indians, wars were few and widely spaced.

Beginning with World War II, though, American presidents grew much more inclined to send our forces to fight in faraway places. The "Vietnam syndrome" supposedly cured that impulse. But it didn't last. Since 1989, University of Chicago scholar John Mearsheimer notes, we have been at war in two out of every three years. We are, in his words, "addicted to war."

Being engaged in combat is the norm. Peace is not really peace—it's just a term we use for that brief interval between invasions.

Obama has a chance to break that pattern, and in his address, he gave hints he might like to. "We, the people, still believe that enduring security and lasting peace do not require perpetual war," he said. "We will show the courage to try and resolve our differences with other nations peacefully."

Hawks regard those as fighting words. The editors of National Review insisted that "it is clear neither that a decade of war is now ending—not in Iraq or Afghanistan, to say nothing of Libya, Yemen, Pakistan, or Mali—nor that the final settlements in Iraq or Afghanistan will secure U.S. security interests." Columnist Bret Stephens of The Wall Street Journal likened Obama to George McGovern and Jimmy Carter.

The idea that Obama would avoid a fight in Syria and Mali probably doesn't alarm the average American, but it shocks the foreign policy establishment—and not just the Republicans. Shadi Hamid of the liberal Brookings Institution criticized the administration last year for giving foreigners the idea "that Obama is a weak president."

To a lot of critics, restraint is appeasement. Many think the United States has the resources and the responsibility to go to war anytime something unwelcome happens abroad.

Obama takes a different view. He completed the Iraq withdrawal and set a deadline to leave Afghanistan. His only significant intervention—using air power in Libya—was brief, limited and low-risk (though constitutionally dubious).

One predecessor his advisers cite is Dwight Eisenhower, who ended the Korean War in his first term and mostly shunned military action in his second. "The appeal of the Eisenhower approach is that it had a big element of turning inward, of looking to rebuilding strength at home, of conserving American power," a senior national security adviser told The New York Times.

Conservation of power makes a lot of sense after that decade of war, whose costs run into the trillions of dollars, not to mention more than 6,600 American lives. Obama has also come to appreciate the limits of U.S might.

When urged to intervene in Syria, according to a disapproving report in The Economist magazine, the president's "response is to ask for evidence that such interventions would make things better, rather than satisfy the urge to 'do something' at the risk of escalating the conflict. His second response is to ask for the price tag." Questions like those usually yield sobering answers.

It may turn out that Obama's real change is not in refusing to use military power but in using a different means—namely, drones. Connoisseurs of irony noted that just hours before he proclaimed the end of our wars, U.S. missiles hit al-Qaida targets in Yemen. But the use of drones falls well short of traditional wars in cost, risk, bloodshed and ease of extrication.

The bigger danger is that he will launch a preemptive strike against Iran, which could lead to a wider war with unpredictable consequences. And though hawks doubt him, he is committed to doing just that if Iran proceeds toward building nuclear weapons.

Obama will deserve credit if he ends the U.S. war in Afghanistan as he did the U.S. war in Iraq. But it's just as important to avoid plunging into another one, and on that prospect, optimism is unwarranted. Addiction to war is like addiction to anything else: The addict always wants more.