When Donald Trump enters the Oval Office, his presidency will begin with a national security challenge that has no precedent — four separate wars where the U.S. military is bombing Islamist extremists.

Presidential transitions in wartime aren't new, and some earlier conflicts were on a much larger scale. President Obama confronted two major wars on his first day in 2009. President Nixon came into office as the Vietnam War raged. President Truman assumed office when Franklin D. Roosevelt died in the final months of World War II.

But Trump, who has no military or foreign policy experience, will be juggling four distinct conflicts on Day 1 — Iraq, Syria, Afghanistan and Libya.

The president-elect has made a sweeping pledge to destroy the Islamic State, the main U.S. focus in three of these countries, and a presence in the fourth (Afghanistan). Yet Trump has not offered specifics and his limited statements have been riddled with contradictions.

"We have some great generals. We have great generals," Trump said in his first big post-election interview, with CBS' 60 Minutes, which aired Sunday night.

The next question addressed his campaign claim that he knows more about ISIS than the generals, and Trump promptly undercut the same U.S. officers.

"Well, I'll be honest with you, I probably do, because look at the job they've done. OK, look at the job they've done. They haven't done the job," Trump said. "Now, maybe it's leadership, maybe it's something else. Who knows? All I can tell you is we're going to get rid of ISIS."

Trump argues it would be folly to unveil his battlefield plans because he wants to keep ISIS and other enemies off-balance. But his vague positions have created legions of skeptics in the military and foreign policy establishment. And given the multiple brush fires awaiting him, Trump will likely be tested early on.

Iraq: The U.S. and its allies are making slow, steady advances against the Islamic State in the northern city of Mosul, the group's last major stronghold in Iraq. If this trend continues into January, Trump could be the beneficiary of Obama's policy, in place since 2014, in which the U.S. bombs from the skies while working with Iraqi partners on the ground.

Trump has savaged this approach as too timid, though the timing may work in his favor, allowing the incoming president to take over with the U.S. and its Iraqi allies gaining ground as ISIS retreats.

"I think destroying ISIS is actually the right goal. It was also the goal of the Obama administration," retired Army Col. Peter Mansoor, a professor of military history at Ohio State University, told NPR.

"However, the question is how you're going to go about it. Beyond just ramping up the bombing campaign, Donald Trump has laid out no specifics," added Mansoor, who questioned Trump's fitness as commander in chief during the campaign.

Also, the hard part for both the Obama and the George W. Bush administrations in Iraq was translating battlefield victories into sustainable political gains.

If ISIS is defeated, what role should the U.S. play in a country that will still be fragile, broke and politically divided? Trump faulted the pullout of U.S. combat troops in 2011 and said America should have "taken the oil." But he has been silent on what he might do.

Syria: Trump's first big military test could come in neighboring Syria, where the U.S. and its partners have launched a campaign to drive ISIS out of its de facto capital, Raqqa.

U.S. policy mirrors the one in Iraq — American airstrikes in coordination with local ground forces. Yet by most every assessment, beating back ISIS in Syria will be a tougher task. The group is more entrenched and multiple players are involved in the Syrian war, including the Syrian government army and its Russian allies.

Trump could be forced early on to choose between a stepped-up campaign against ISIS and limiting U.S. involvement in the country.

And defeating ISIS would be only part of the equation. The Obama administration says Syrian President Bashar Assad also must go. Trump appears much less concerned about Assad remaining in power.

"We cannot tell anything about what he's going to do," Assad told Portugal's state television in an interview that aired Tuesday. But, he added, if Trump is "going to fight the [ISIS] terrorists, of course we are going to be [an] ally, natural ally in that regard with the Russians, with the Iranians, with many other countries."

Afghanistan:The longest war in U.S. history, at 15 years and counting, could also claim to be the most forgotten. The war was a nonfactor in the campaign, and Trump has not signaled that he wants to step up the U.S. investment there.

However, the Taliban remain a formidable force, and Obama repeatedly put his own withdrawal timetable on hold rather than risk losing hard-won gains.

Obama will leave behind 8,400 U.S. military personnel in Afghanistan, the largest U.S. force in any war zone. The Americans have carried out thousands of sorties this year and last, even though Obama declared a formal end to combat operations at the end of 2014.

Afghanistan offers no appealing choices. There's no prospect of military success in the short term, and a Trump decision to pull back or to stay on both carry risks. This point was driven home on Saturday when a Taliban suicide bomber penetrated the highly fortified Bagram Air Base, north of Kabul, killing four Americans and wounding 16.

Libya:Though the U.S. air campaign receives little notice, the military has bombed in Libya 350 times since August, targeting ISIS forces in the coastal city of Sirte.

Trump repeatedly criticized Hillary Clinton for advocating in support of the 2011 bombing campaign that ousted dictator Moammar Gadhafi. With the country now mired in civil war, Trump has described U.S. involvement in Libya as a failure.

So will he scale back — leaving the Islamic State as a significant player — or take additional action in an attempt to defeat the extremists?

That's an open question. And just one of many, according to skeptics.

"I am willing to wait and see. He's the president-elect, fairly elected. And I think we need to give him space to let his policies play out," said Mansoor, the Ohio State professor. "However, I do not take back anything I said during the campaign. He's going to be a potentially dangerous president. And I hope I'm wrong."

Greg Myre is the international editor of NPR.org. Follow him on Twitter @gregmyre1.

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