WASHINGTON (AP) — Before he became president, Donald Trump rarely talked about Afghanistan. When he did, he often called for a swift end to America's longest war.

But on Monday, Trump announced to the nation that the war will press on, with no clear end in sight. His prime-time address cemented his standing as the third American president to oversee a conflict that has vexed Republicans and Democrats alike.

He declared: "In the end, we will win."

Trump's plans, while vague at times, amount to a victory for the military men increasingly filling Trump's inner circle and a stinging defeat for the nationalist supporters who saw in Trump a like-minded skeptic of U.S. intervention in long and costly overseas conflicts. Chief among them is ousted adviser Steve Bannon, whose website Breitbart News blared criticism Monday of the establishment's approach to running he war.

"What Does Victory in Afghanistan Look Like? Washington Doesn't Know," read one headline.

Now Trump leads Washington and that question falls for him to answer. He has seized on his mantra "America First," but so far has spent little time explaining how that message translates to U.S. involvement in a war across the globe, likely for years to come.

"Most people agree to make this work, to be successful, we're going to need to be in Afghanistan a few more years at least," said retired Lt. Gen. Thomas Spoehr, director of the Center for National Defense at The Heritage Foundation. "That is typically not President Trump's style. He likes to get a quick victory."

President George W. Bush plunged U.S. troops into Afghanistan after 9/11 but the war languished as American military attention focused on Iraq. President Barack Obama ratcheted up to 100,000 troops early in his administration, but hoped to wind down the war before he left office. He ultimately conceded that security concerns would require him to hand off the war to another president.

Trump spoke boldly Monday of victory, defining success as "attacking our enemies" and "obliterating" the Islamic State. Winning the war, Trump said, would mean preventing the Taliban from taking over Afghanistan and stopping mass terror attacks.

But in meeting those markers, Trump faces many of the same challenges in Afghanistan that have bedeviled his predecessors and left some U.S. officials deeply uncertain about whether victory is possible — and if it is, what such a victory would entail.

Afghanistan remains one of the world's poorest countries and corruption is embedded in its politics. The Taliban is resurgent. And Afghan forces remain too weak to secure the country without American help.

"When we had 100,000 U.S. troops in Afghanistan, we couldn't secure the whole country," said Ben Rhodes, who served as Obama's deputy national security adviser.

The U.S. currently has about 8,400 troops in Afghanistan. Pentagon officials proposed plans to send in nearly 4,000 more to boost training and advising of the Afghan forces and bolster counterterrorism operations against the Taliban and an Islamic State group affiliate trying to gain a foothold in the country.

To reach his decision, Trump held extensive discussions with top advisers in the Pentagon, the State Department and the intelligence community, and heard directly from Defense Secretary Jim Mattis, national security adviser H.R. McMaster and Vice President Mike Pence. It was a more deliberate process than has been typical for Trump, who has shown a propensity to make impulsive decisions.

Trump initially resisted his advisers' urging to send more U.S. troops to Afghanistan and said his instinct was to bring the war to a close. But as he addressed the nation, he acknowledged a reality that so many of his predecessors have learned.

"I heard that decisions are much different when you sit behind the desk in the Oval Office," Trump said.

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EDITOR'S NOTE — Washington Bureau Chief Julie Pace has covered the White House and politics for The Associated Press since 2007. Follow her at http://twitter.com/jpaceDC .

Ken Thomas has covered the White House and national politics for the AP since 2011. Follow him at http://twitter.com/kthomasDC .