President Trump says he wants a swift and complete victory over the Islamic State, and he inherits the battle at a moment when the extremist group is losing ground in Iraq and Syria. The group's self-declared caliphate is looking increasingly fragile.
Could 2017 be the year the U.S. and its allies break the back of ISIS?
Progress is being made in the war against the Islamic State, according to analysts. But they caution that the U.S. is likely to face a recurring challenge in the Middle East: how to turn battlefield gains into a comprehensive political solution.
"The quickest way to lose against ISIS would be declaring victory too soon," says Jessica Lewis McFate of the Institute for the Study of War in Washington, D.C. "ISIS is fighting a multigenerational war, and we need to think that way as well."
Trump heads to the Pentagon on Friday for his first meeting with the Joint Chiefs of Staff, and the war with ISIS is expected to be at or near the top of the agenda.
Here are several key questions to watch this year:
1. Will Trump take a radically different approach than Barack Obama?
Their rhetoric is diametrically opposed, but it's not clear how that will translate into policy.
Obama's watchwords were patience, restraint and a limited American role. He took a lot of heat from Republicans who said he didn't do enough to roll back ISIS. Yet since he ordered the U.S. air campaign in the summer of 2014, ISIS has lost most of its territory in Iraq, and chunks in Syria as well.
Trump's inaugural address didn't mention ISIS by name, though he said his administration would "unite the civilized world against radical Islamic terrorism, which we will eradicate completely from the face of the earth."
Trump hasn't laid out details, such as whether he wants to add to the roughly 6,000 American military personnel in Iraq and Syria, where they are training, advising and carrying out the air campaign. They're often close to the front lines or soaring above them, but they're not supposed to be in ground combat.
Escalating the air campaign is an option, with caveats.
After some 17,000 U.S. airstrikes over the past couple of years, ISIS targets are increasingly hard to find, and ISIS members often seek shelter by clustering in civilian areas.
"There are not a whole series of targets we have simply not hit. That's not the case," Deborah James, who just stepped down as Air Force secretary, told U.S. News and World Report. "What we have been very careful about is making sure we know what we're hitting, and taking care to hit what we intend to hit."
2. Should Iraq and Syria be viewed as two separate wars?
The U.S. focus is on ISIS in both countries, but the wars are at different stages right now.
ISIS has been greatly weakened in Iraq. The northern city of Mosul is its last stronghold, and after four months of fighting, ISIS has been driven out of the eastern half of the city on the eastern bank of the Tigris River. A major battle is looming in the densely packed western part of the city, which could also involve months of fighting.
If ISIS is driven out of Mosul, it would be a diminished threat, though it could still press on with its campaign of car bombs that target Baghdad and several other key cities.
In Syria, ISIS has lost ground but still controls large parts of eastern Syria, including Raqqa, its de facto capital in the desert.
The U.S. is working with Arab and Kurdish fighters, and they have come as close as 17 miles from Raqqa. But all forecasts point to a long, hard slog to uproot ISIS. And ISIS is just one faction in the hugely complicated Syrian war.
"ISIS is still in a very good position in Syria because everyone else is in a bad position," said Lewis McFate. "Right now, it's hard to see a good political future for any of the actors."
3. How is ISIS responding in its weakened state?
The Islamic State is ambitious and unpredictable. Its ambition was on display during its rapid expansion in 2014, as it gained men, money and territory, seemingly by the day.
All these resources have been shrinking for the past year or more. ISIS has more trouble attracting new recruits, partly because Turkey has tightened its border with Syria, the main gateway for foreign fighters.
When ISIS was surging, it paid regular salaries to its fighters. The group looted Iraqi banks and sold oil from Syrian wells it captured. Those sources are drying up after sustained attacks.
"We are destroying [ISIS'] economic base," Brett McGurk, Obama's point man on the group, said last month.
"Their fighters are not getting paid, and we have multiple indications of that," added McGurk, who has remained in his post during the early days of the Trump administration.
However, the group has been full of surprises and that's why it's expected to remain dangerous.
Major terror attacks in Turkey and Europe have demonstrated the group's reach, and as it loses ground at its core in the Middle East, lashing out abroad is a way to show it's still relevant.
Counterterrorism officials warn that fighters in Syria and Iraq could flee from the collapsing former Islamic State and continue to pose a terror threat in the West.
ISIS also has a habit of returning to places where it was dislodged. ISIS recaptured the ancient Syrian town of Palmyra last month, several months after it had been driven out. For good measure, it recently destroyed part of Palmyra's most famous Roman ruins.
4. What about "the day after?" What's the plan if ISIS is defeated?
In Iraq, the path ahead is relatively clear. Not easy, but clear.
Obama's approach envisioned an Iraqi government and military that would own the fight against ISIS. Iraqis will play the lead role and that will give them the strength and credibility to take control after the fighting.
The Iraqi government will have to rebuild cities, unify the country and guard against a return to sectarian feuds. Previous governments failed miserably, and this one might, too, but at least there's broad agreement on the aim.
In Syria, the puzzle has many more pieces, and it's not clear if any of them fit together.
If the U.S. and its allies dislodge ISIS, some party would still need to take political control in eastern Syria. If the U.S. doesn't want to occupy the region — and there's no sign it does — the Trump administration would have to find someone who could hold it.
The limited options would include the hodgepodge of local factions that are at odds with President Bashar Assad's government, which might have its own designs on the region.
And relative calm in eastern Syria doesn't mean peace will break out in the more heavily populated western part of the country. That's where the Syrian government, with its Russian and Iranian allies, is still at war with multiple rebel groups.
Greg Myre is a national security correspondent. Follow him on Twitter @gregmyre1.