Washington ? President Obama certainly didn’t go looking for another war in the Middle East. Indeed, he contorted himself almost to the breaking point to avoid one. But as he explained to the country Wednesday night, he had no choice but to respond with “strength and resolve” to the barbarous Islamic State that is ravaging Iraq and Syria.

Obama’s decision to combat the Islamic State offers him a chance to reset American leadership and his own presidency after growing doubt at home and abroad about what, if anything, he was willing to fight for. His innate cautiousness is now actually a reassurance that he’ll fight this war sensibly, partnering with allies in the region, in a way that doesn’t needlessly exacerbate America’s problems with the Muslim world.

Stephen Hadley, who was national security adviser for President George W. Bush, is hardly a cheerleader for Obama. But he gave the president high marks for “a good speech” that explained the threat and what he was going to do about it. Hadley noted that Obama’s stance as a reluctant warrior will help him reassure foreigners and Americans alike that this isn’t a reckless, unilateral U.S. crusade.

“He will put together a coalition, and he will try to keep them out front,” said Hadley in an interview. “It will still be an American fight, but it will look less like one, and that’s actually a strength. People will be less worried that it’s a slippery slope if he’s in charge because he’s reluctant to be where he is.”

For a White House that has often struggled to execute foreign policy cleanly, this week has been a notable exception. The rollout was smooth: An Iraqi unity government was formed last weekend; the president dined Monday night with foreign policy experts; he briefed congressional leaders Tuesday; then he addressed the country. Obama’s team must maintain that momentum.

Obama has taken a pounding over the past year for a reticent, risk-averse foreign policy that some characterized as evidence of weakness and retreat. Part of the criticism has been deserved: Obama should have ramped up assistance to the Syrian opposition much earlier; he should have rejected the polarizing, sectarian Iraqi Prime Minister Nouri al-Maliki long ago. These two mistakes allowed the Islamic State to feed off Sunni rage in Syria and Iraq, so that it became more toxic. This disaster was not inevitable.

Obama’s preference for working through allies, derided by critics as “leading from behind,” may offer an advantage now. America can use its air power to degrade the Islamic State because it has support from allies in the region — Saudi Arabia, Turkey, Jordan, the United Arab Emirates and (implicitly) Iran. The U.S. can avoid major ground combat to the extent that it recruits other boots on the ground, from its regional allies.

This Muslim cover is essential if the U.S. is going to fight the next round of the campaign against jihadists without making the mistakes of the past decade.

Another unlikely opportunity for Obama is that the Islamic State provides a common enemy for erstwhile antagonists, such as Saudi Arabia and Iran, or Turkey and Iraqi Kurdistan. Already, there are little hints of rapprochement: Iran’s deputy foreign minister recently visited Saudi Arabia; Hezbollah’s pet newspaper in Beirut just published a rare plaudit for Sunni leader Saad al-Hariri. Obama rightly hopes that a joint fight against the Islamic State may open space for regional dialogue that may gradually bridge the Sunni-Shiite sectarian chasm through which the poison flowed.

The shakiest aspect of the policy is the Syria strategy. Obama is pinning his hopes on a moderate opposition that has stumbled badly over the past two years. The U.S. will bomb the Islamic State’s havens in Syria, but can the moderates seize and hold ground as the jihadists retreat? Probably not at first, but they’ll do better with U.S. training. This is a fight that’s likely to last years, not months.

A final advantage for Obama is that he seems to understand the historic moment in which the nightmare of the Islamic State has arisen. The old order in the Middle East is collapsing and the new one hasn’t yet emerged. This creates space for religious fanatics who feed on the populist rage of an untethered region. Amid this anarchy, Obama is seeking to prevent the worst outcome, without the false hope that he’s creating a shining new democratic order. This is still Iraq, but the illusions of 2003 are gone.