PROVIDENCE, R.I. — Many veterans who fought in America’s longest war say it’s reassuring that President Donald Trump reversed his past calls for a speedy exit from Afghanistan and won’t pull troops out under a strict deadline.

They don’t want the sacrifices they’ve made to be in vain, though some worry the administration’s strategy is too vague to lead to victory.

Trump recommitted the United States to the 16-year-old war in a national address Monday, announcing a plan that includes sending up to 3,900 additional U.S. forces to join the 8,400 troops currently in Afghanistan.

The first deployments could take place within days. The strategy shifts away from a “time-based” approach and instead focuses on linking assistance to results and to cooperation from the beleaguered Afghan government, Pakistan and others.

Marine veteran Peter James Kiernan praised Trump for not pinning withdrawal to a timeline that enemy fighters could just wait out, but he expressed concern about the lack of specifics.

“For the moment, I think our partners in Afghanistan will take it as a reaffirmation that we’re still committed to helping them, which is the biggest benefit,” said Kiernan, who spent nine months in Afghanistan and recently graduated from Columbia University. “But there’s no guarantee how long that’ll last, and a lot of things in this presidency are subject to change quickly.”

Former Marine Capt. Derek Herrera, a Bronze Star recipient left paralyzed by a sniper’s bullet in Afghanistan, agreed that withdrawal should not have a deadline but said there also needs to be a conversation outlining what success would look like and how to reach that.

Thomas Porter, a military reservist who served in Afghanistan, said he’s encouraged that Trump appears to have listened to military commanders instead of going “with his gut.” Porter, the legislative director for Iraq and Afghanistan Veterans of America, said he’s waiting to see how steady the administration will be in this new strategy and how returning veterans will be treated.

Former Army Capt. Andrew J. Brennan, though, doubts the strategy will succeed given the American public’s war fatigue.

“The United States will never win a war without the commitment of its populace, but the will of the American people does not support this war effort,” said Brennan, who flew combat missions in Afghanistan.

Trump said the U.S. was intent on “killing terrorists” rather than “nation building.”