American forces "do not and will not have a combat mission," Obama told troops at the U.S. Central Command headquarters here. "They will support Iraqi forces on the ground as they fight for their own country against these terrorists."
He made that pledge a day after Gen. Martin Dempsey, the chairman of the Joint Chiefs of Staff and the military's top officer, described for a Senate panel the challenges of fighting the militants without combat troops on the ground.
Obama also deliberately has specified that U.S. combat troops would not be deployed to "fight" -- a distinction that allows for the possibility that U.S. special forces might be used in a rescue mission, as was the case this summer in the failed attempt to retrieve U.S. hostages being held by Islamic State militants in Syria.
"As your commander in chief, I will not commit you … to fighting another ground war in Iraq," he said. "After a decade of massive ground deployments, it is more effective to use our unique capability in support of partners on the ground so they can secure their own countries' futures."
He listed the commitments other nations have already made, asserting that more than 40 have offered help for the broad campaign.
France and Britain are "flying with us over Iraq," he said, and Saudi Arabia has committed to host training for regional fighters.
"Arab nations have agreed to do what they can to strengthen Iraq's government," he said, and others have agreed to help "stem the flow of foreign fighters into and out of" the region.
Those tools aren't as easy to see in the short term, said Alterman, but "they present the only path to victory: crippling the organization's networks, denying the group safe haven and undermining the conditions that make it attractive to potential recruits."
"As Gen. Martin Dempsey suggested before the Senate, they may beget even more military action," he said. "Military instruments are enough to fight, but in this battle, they are not nearly enough to win."
During a week of events meant to bolster Obama's foreign policy credentials with the public, the White House also saw evidence of the challenges facing the president as he tries to help fellow Democrats keep control of the Senate in the fall elections. A New York Times/CBS News poll out Wednesday showed his approval ratings on par with those of Republican President George W. Bush near the 2006 midterms -- when Democrats swept both houses of Congress.
But the latest poll raises questions about whether that translates into support for the president himself. The poll's 34% approval rating for his handling of foreign policy is a record low for him, though it isn't as low as Bush's eventual low of 25%.
And Obama's 41% rating for his handling of terrorism is lower than any score on that issue for both him and his predecessor.
On Wednesday, the president reiterated the parts of his strategy to take on the militants that have drawn criticism and insisted that the old way of fighting in the Middle East will not work.
"When we do things alone, and the people of those countries aren't doing it for themselves, as soon as we leave we start getting the same problems," he said. "We've got to do things differently."