The election of Donald Trump as commander-in-chief poses a real risk that decades-old norms of defense and foreign policy will be upended — with uncertain consequences at home and abroad.
The Republican real estate mogul has claimed he knows more than the generals and vowed to fire en mass the top military brass. He's suggested that allies like South Korea and Japan should build up their own nuclear arsenals as part of a more isolationist "America First" foreign policy. He similarly warned that the U.S. would not protect NATO allies in Europe if they didn't pay their share. And he says he wants to employ torture to gather intelligence from terrorist suspects.
But at the same time, Trump's lack of details on how he would proceed — and proclivity to deny that he even made many of the pronouncements in the first place — give national security veterans hope that the brash, tough-talking New Yorker can be forced to pursue a more establishment, less half-baked approach. And that the inherent checks on the president combined with congressional gridlock will temper his most dramatic policy proposals.
He'll quickly learn how limited the executive branch's reach can be without congressional approval, defense analysts and lobbyists say, just as President Barack Obama was stymied on his campaign promise of closing the U.S. military prison at Guantanamo Bay, Cuba.
"He's going to be frustrated by a lot of things, about why he can't make certain things happen without Congress," said Michael Herson, a longtime defense lobbyist at American Defense International.
Trump is also likely to be confronted with one or more curveballs early in his administration. One likely crisis, according to a number of defense officials: more nuclear saber rattling by North Korea to get concessions from the new administration.
One of Trump's clearest promises, though, has been well-received by the defense establishment. His repeated call for a major reinvestment in the U.S. military — including ramping up the number of U.S. troops, warships and fighter jets — was music to the ears of military contractors, and their boosters have pushed hard in recent years, to little avail, for major increases in military expenditures and more predictable budgets.
To achieve it, however, he'll have to convince members of both parties in Congress to lift the spending constraints imposed by the Budget Control Act. And that will be no easy task.
"Until that budget mess gets sorted out, trying to do anything sensible in the Pentagon is going to be a huge challenge just because of the uncertainty associated," said former Defense Secretary Robert Gates, a Republican who opposed Trump's candidacy.
Finding a way to lift the spending caps, Gates argued, "has a gigantic impact on every single thing, from ... personnel to the size of the force, to the weapons they can afford, and so on."
Trump will also have to mend his relationship with Sen. John McCain (R-Ariz.), the chairman of the Armed Services Committee, whose military record he denigrated on the campaign trail. McCain, meanwhile, unendorsed Trump late in the campaign over his disparaging comments toward women.
Trump's candidacy was also opposed by many members of the Republican national security establishment, who could now find themselves in exile — at least for a time.
And it will leave the new president with a comparatively slim roster to turn to in filling key posts.
Among the Republican defense officials who could join the Trump administration: Sen. Jeff Sessions (R-Ala.), a close adviser, has been discussed as a potential defense secretary. And former National Security Adviser Stephen Hadley and former Sen. Jim Talent (R-Mo.) have also been mentioned as potential national security contenders.
Top Trump confidante retired Lt. Gen. Mike Flynn, the former director of the Defense Intelligence Agency, would need a waiver from Congress to become defense secretary, as the law requires retired military officers to wait seven years before becoming the civilian leader of the Pentagon. But Trump's chief military adviser is likely to wind up in a senior administration post, potentially national security adviser. And other early endorsers, like Rep. Duncan Hunter (R-Calif.) could be in line for top posts as well.
Here's a closer look at how the U.S. military posture might shift after the new president takes office Jan. 20:
Trump has vowed to defeat the Islamic State quickly, though he has provided few details.
During the campaign, he repeatedly criticized the offensive in Mosul, Iraq, for being too obvious, arguing for the element of surprise and keeping military plans under wraps — a notion that military experts have roundly denounced as irrelevant to such a massive operation.
While criticizing them in nearly the same breath, Trump in September said he would instruct top military leaders to formulate a plan within 30 days of taking office to defeat the Islamic State. And he's expressed some support for using U.S. ground troops to do it.
"We really have no choice, we have to knock out ISIS," Trump said during a March primary debate. "I would listen to the generals, but I'm hearing numbers of 20,000-30,000."
Trump has suggested he'll be able to defeat the Islamic State quickly, but he's given no details for how he would change the current U.S. strategy, in which U.S. forces are supporting Iraqi troops and U.S.-backed Syrian rebels to go after ISIL in Mosul and Raqqa.
"I could see Trump potentially doing something dramatic, like, 'Alright we're done, we're pulling everybody out,'" said Rep. Adam Smith of Washington state, the top Democrat on the House Armed Services Committee. "But at the same time, he's said over and over again that this should be easy, we should be able to win, we should be able to take care of this. My sense is that rhetoric will not turn into action."
The president-elect also maintains he has no interest in increasing U.S. involvement in the Syrian civil war, arguing the U.S. military should only be fighting ISIL there because whatever would come after Syrian President Bashar Assad could be even worse.
"What we should do is focus on ISIS. We should not be focusing on Syria," Trump told Reuters in an interview last month. "You're going to end up in World War III over Syria if we listen to Hillary Clinton."
While he hasn't said if he'd submit a new authorization for the use of military force in the campaign against the Islamic State — like Obama did in 2015, unsuccessfully — Trump has said he'd have "no problem" asking for a formal declaration of war against ISIL.
But while Republicans and Democrats alike have advocated for a new legal document to govern the campaign, key details like the length of the authorization and whether to limit the use of ground troops have stymied efforts at a new AUMF.
Trump's plans for the military will likely require a major increase in defense spending. He's proposed a massive expansion to "rebuild" a military he's declared has been decimated by sequestration.
Trump proposed increasing the size of the active-duty Army to 540,000, up from the current 475,000, and boosting the Marine Corps to 36 battalions. And he's called for a 350-ship Navy, well above the current fleet of just less than 280.
"His statements so far definitely seem to indicate a desire to invest more in national defense," said Justin Johnson, a defense analyst with the conservative Heritage Foundation.
Trump has called for eliminating only the defense spending caps set under the Budget Control Act. But that military blueprint — and the budget plan to pay for it — would be difficult to implement as Democrats seeking higher funding for domestic spending would almost certainly oppose a defense-only budget increase.
At times during the long campaign, Trump's own statements on defense spending have been contradictory.
He's said he'd offset his military buildup with cuts to unnecessary weapons systems and pet defense projects pushed by Congress and "special interests." But he's likely to be swiftly overturned by lawmakers, who hold the power of the purse and have pushed back on several recent attempts by the Pentagon to save money by retiring aging platforms.
The president-elect's relationship with Russian President Vladimir Putin will be closely watched around the world.
Trump has praised Putin as a stronger leader than Obama and suggested he would be able to improve the frosty relations between Washington and Moscow.
"If Russia and the United States got along well and went after ISIS, that would be good," Trump said during this fall's third presidential debate.
Trump's comments about Putin — as well as suggesting Russia wasn't behind hacks of the Democratic National Committee — were a frequent attack line for Democrat Hillary Clinton during the campaign, who argued that Putin was trying to help get Trump elected "because he would rather have a puppet as president of the United States."
Friendly or not, Trump will have to deal with Moscow's aggression in Syria, as well as the prospect of further Russian action in Eastern Europe. And defense analysts are skeptical Moscow will change just because Trump is in the Oval Office.
"A modest tweak to that policy is not going to be enough to persuade Russia to work with us," said Michael O'Hanlon, a senior fellow at the Brookings Institution.
As president, Trump will inherit an aging nuclear arsenal with estimates for overhauling the weapons ranging as high as $1 trillion.
The Defense Department has pushed to modernize all three legs the nuclear triad — land-based missiles as well as new fleets of ballistic missile submarines and long range bombers. And while Pentagon officials contend the wholesale modernization is affordable, caps on defense spending could hamper the effort.
Trump has argued U.S. nuclear weapons have been neglected while Russia has built up its capacity, sharply criticizing the New START treaty.
"Our nuclear program has fallen way behind and they have gone wild with their nuclear program," Trump said in the second presidential debate. "Our government shouldn't have allowed that to happen. Russia is new in terms of nuclear and we are old and tired and exhausted in terms of nuclear."
Smith predicted Trump and Republicans in Congress will seek to "spend an obnoxious amount of money on a level of deterrence that we don't need."
Trump has also sharply criticized the Iran nuclear deal and efforts to contain North Korea's nuclear program.
Now, he'll have to reconcile his statements that caused Democrats to label him dangerous with the nuclear launch codes, including expressing openness to countries like Japan and South Korea to defend themselves with their own nuclear weapons.
Asked about changes to the policy of nuclear first use during the first presidential debate, Trump said he "would certainly not do first strike."
Trump's "America first" campaign will certainly leave many U.S. allies nervous as he takes office.
Like his views on trade, Trump has argued that U.S. military posture abroad is a raw deal for the U.S., with allies taking advantage of U.S. military might without paying their fair share.
Over the past year, Trump has called NATO "obsolete" and suggested in a July interview with The New York Times that he might not come to the aid of NATO members who were attacked — a requirement under's NATO Article 5 assertion of mutual defense— unless they have "fulfilled their obligations to us."
The Obama administration has pressed for European allies to meet their spending requirements on NATO, but Trump could pull back on U.S. spending there.
And Trump has suggested pulling back U.S. forces in locations like South Korea and Japan. "South Korea is very rich, great industrial country, and yet we're not reimbursed fairly for what we do," Trump said in a March interview with The Washington Post.
Another area where foreign capitals — and U.S. diplomats — are watching with piqued interest: who Trump opts to appoint as his ambassadors. Career diplomats have already expressed concerns about their future in a Trump administration.