The third in a series of articles examining major issues facing President-elect Donald Trump following his inauguration.

President-elect Donald Trump has vowed to employ a national security strategy of “peace through strength” as the nation’s next commander-in-chief — proposing to boost military spending while re-evaluating the country’s longstanding international alliances.

Foreign policy and counterterrorism experts say the real estate mogul, who during the campaign proclaimed he knew more about the Islamic State terrorist group than “the generals do,” will soon be confronted with the reality that change is deliberately slow-moving in the deeply methodical worlds of military planning, intelligence gathering and diplomacy.

“The national security bureaucracy like the rest of the federal bureaucracy is massive,” said Jeffrey Engel, director of the Center for Presidential History at Southern Methodist University in Dallas. “It does not turn quickly, and more importantly it’s filled with smart people who have already been working 24/7 on these difficult problems for years. If there were solutions to these problems they would have already come up with them by now, which means they are unlikely to radically change direction over night.”

In the weeks before taking office, Trump has turned to Twitter and media interviews to signal his desire for a new era of U.S. international relations. Former foes have been regarded as friends, such as his supportive comments toward Russian leader Vladimir Putin. Longtime alliances have been tested, such as European leaders conflicted over how to respond to his recent remarks questioning the European Union’s purpose and labeling the 67-year-old NATO peacekeeping alliance “obsolete” during an interview with the Times of London and Germany’s Bild newspaper.

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“This is clearly someone who sees being unpredictable as an advantage . . . he’s going to try to do the opposite of what is conventional wisdom in foreign policy,” said Jeremi Suri, a professor of global leadership and public policy at the University of Texas at Austin. “Conventional wisdom has always been that consistency, especially for a strong power, is important . . . He doesn’t operate that way, that’s just his style . . . That’s going to be a big shift.”

Corri Zoli, director of research for the Institute for National Security and Counterterrorism at Syracuse University, said Trump’s tweets and public comments signal at the United States returning to the military posture of “deterrence.”

“Our traditional posture has been one of deterrence making sure that our military and our institutions and all of our instruments of national power were so strong . . . ,” Zoli said. “This last administration has really backed off deterrence. Some people describe that strategy, that the Obama administration has used, and to certain degrees the Clinton administration as well, as leading from behind. This idea that you can sort of step back a little bit, promote engagement with the world, instead of showing people a hard face . . . this is shifting now, I think we’re going to see a significant return to that default mode of deterrence under Trump.”

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Military force

Trump, in a policy speech delivered last September in Philadelphia, said he would seek to increase the size of the military — including boosting the number of “combat-ready” Army troops to “around 540,000” soldiers compared to the 490,000 currently enlisted.

He also said he would push for a defense budget that adds 74 Navy ships and submarines to the country’s current fleet, and 87 additional Air Force fighter aircraft.

“We will also seek to develop a state of the art missile defense system,” Trump said.

Suri, author of the book “The Impossible Presidency,” said that while Trump may find “some support” for his military agenda in the Republican-led Congress, he may also find it difficult to receive support for more military spending as he also proposes a massive infrastructure plan aimed at creating jobs.

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“He’s going to want to prioritize his domestic agenda and the infrastructure spending,” Suri said. “The same members of Congress who are willing to spend money on the military don’t want to raise taxes, they don’t want to raise the deficit, they don’t want to spend a ton of money on the infrastructure, so he’s going to have to find a compromise.”

Fight against ISIS

On the campaign trail, Trump said he would “crush and destroy” the Islamic State terrorist group, but some of his counterterrorism proposals, including banning foreign Muslims from entering the United States, have been widely condemned by civil rights groups who argue the measures and his rhetoric unfairly target law-abiding Muslims.

Trump’s nominee for Secretary of Homeland Security, retired Marine Gen. John Kelly, also indicated he was unsupportive of such an approach, when asked to clarify his position during his Senate confirmation hearing last week.

“I don’t think it’s ever appropriate to focus on religious factors,” Kelly said. “I don’t agree with registering people based on ethnic or religion or anything like that.”

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Zoli, of Syracuse University, said she believes Trump’s choice of Kelly and retired Marine Gen. James Mattis for Secretary of Defense, two battle-tested generals who are willing to oppose his controversial positions, indicates some level of willingness to seek guidance from two figures widely respected in national security circles. Mattis is often referred as the “Warrior Monk,” because he is a well-read scholar and someone who prefers diplomacy over combat to resolve major conflicts.

During his Senate confirmation hearing last week, Mattis told the panel, “We have to deliver a very hard blow against ISIS in the Middle East so there is no sense of invulnerability or invincibility there.”

Intelligence community

While Trump has had a rocky relationship with the U.S. intelligence community — spurred by his initial skepticism of their conclusions that Russia orchestrated a series of cyberattacks against the United States — his nominee to lead the Central Intelligence Agency, Rep. Mike Pompeo of Kansas, assured lawmakers during a Senate confirmation hearing last week that the agency would continue to pursue “foreign intelligence with vigor no matter where the facts lead.”

Pompeo, breaking from Trump’s generally supportive position toward Putin, called Russia and China “sophisticated adversaries,” and said the United States is facing one of the most “complicated” periods in national security as it confronts domestic terror threats inspired by the Islamic State.

“This is the most complicated threat environment the United States has seen in recent memory,” Pompeo said.