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Steeling the nation for a long fight, President Barack Obama vowed Wednesday to take out the militants of ISIS with U.S. air power and help from the world — but without American combat troops.

He said that the campaign would be steady and relentless, and said he would not hesitate to strike ISIS inside Syria. But he stressed that it would be different from the years-long wars in Iraq and Afghanistan. He compared it instead to targeted American strikes to wipe out terrorists in Yemen and Somalia.

“We took out Osama bin Laden,” the president said — with the clear message that ISIS would be next.

“I have made it clear that we will hunt down terrorists who threaten our country, wherever they are,” he said. “This is a core principle of my presidency: If you threaten America, you will find no safe haven.”

Speaking from the White House, one day before the Sept. 11 anniversary and days after ISIS militants beheaded two Americans, the president promised to “lead a broad coalition to roll back this terrorist threat.”

U.S. role

Obama announced that an additional 475 American military personnel would be deployed to help Iraqi and Kurdish forces with training and intelligence. Of those, 150 will be embedded with the Iraqi military, serving as advisers but not engaging in combat themselves, defense officials told NBC News after the speech.

Once those 475 have arrived, the Pentagon said, the United States contingent in Iraq will number 1,600.

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In his address, Obama stressed that the American military presence would not be for combat.

“We will not get dragged into another ground war in Iraq,” he said.

In an NBC News-Wall Street Journal poll released this week, 40 percent of respondents said that U.S. military action against ISIS should be limited to airstrikes. Another 34 percent say it should include airstrikes and combat troops. And 15 percent say military action should not be taken.

The coalition

Obama pledged to build an international coalition to defeat ISIS. Secretary of State John Kerry was in Iraq on Wednesday and will travel to Saudi Arabia on Thursday to meet with Middle Eastern allies.

Obama said the United States needs more partners, making special note of Arab nations who can mobilize Sunnis in Iraq and Syria to drive ISIS fighters from their lands.

“We stand with people who fight for their own freedom, and we rally other nations on behalf of our common security and common humanity,” he said. American leadership, Obama said, was “the one constant in an uncertain world.”

The stakes

The president said that the United States had not detected “specific plotting against our homeland.”

But he noted that thousands of foreigners, including Europeans and Americans, have joined ISIS, and he said that ISIS fighters could one day return to their countries and try to stage attacks.

“I know many Americans are concerned about these threats,” he said. “Tonight, I want you to know that the United States of America is meeting them with strength and resolve.”

He mentioned the more than 150 airstrikes carried out already by the United States to fight ISIS in Iraq, including some that helped break the siege on an Iraqi mountain where thousands of religious minorities were trapped.

Syria

Signaling an expansion of the campaign, Obama said: “I will not hesitate to take action against ISIL in Syria, as well as Iraq.” ISIL is alternative name for ISIS. Obama vowed that the United States would “hunt down terrorists who threaten our country, wherever they are.”

Obama said it was imperative to strengthen opposition fighters in Syria — who are battling both ISIS and the regime of President Bashar Assad. He said the rebels would be “the best counterweight” to ISIS.

— Erin McClam