Trump's election would bring on "the greatest crisis in civil-military relations since the civil war."

[W]hen Trump has weighed in on national security questions, his remarks often reveal either ignorance or disdain for military expertise and the codes of conduct that govern the armed forces. “I know more about ISIS than the generals do. Believe me,” he boasted in one speech, adding, "I’ve had a lot of wars of my own. I’m really good at war." His foreign policy prescriptions include proposals to “bomb the shit out of ISIS,” to “take out” the families of ISIS members and to torture terrorism suspects. (“Would I approve waterboarding? You bet your ass I would,” he told one crowd. “And you know what? If it doesn't work, they deserve it anyway, for what they're doing.”) When it was pointed out that soldiers couldn’t legally carry out those last two actions, Trump was unconcerned. "They're not going to refuse me. Believe me.” (He walked back that last statement the next day.) The Geneva Conventions, he recently observed, have made American soldiers “afraid to fight.”

Trump’s pronouncements on foreign policy, combined with his years of broadsides, have set off a very real fear within military circles about what might happen were he to become president. In the last two months, I spoke with dozens of people in the national security realm—current and retired officers, veterans of the wars in Iraq and Afghanistan, and former White House, State Department, Pentagon and CIA officials. The words they used to describe their mood: Terrified. Shocked. Appalled. Never before, they say, has a candidate gotten so close to the White House with such little respect for the military.

One former Marine infantry officer described Trump as a “fake-bake-ing chicken hawk.”

“He completely misunderstands the military profession that he would head if he were the president,” said Robert Killebrew, a retired colonel who served in the Army for more than 30 years. Others were less polite. In a pair of ads produced by the American Future Fund, a retired Special Forces commander named Michael Waltz calls Trump a draft-dodger who “hasn’t served this country a day in his life,” and a Vietnam veteran, Tom Hanton, says that Trump’s quip about POWs was “the most infuriating comment I think I’ve heard from a politician in my entire life.” One former Marine infantry officer described Trump to me as a “fake-bake-ing chicken hawk” whose “knowledge of the Middle East could be trumped (sorry) by your average Georgetown sophomore.”

Trump’s chosen foreign policy advisers—which include a 2009 college graduate who touted his experience in the Model U.N. on his online résumé and another who used Kanye West lyrics to make arguments on his foreign policy blog—have only stoked these anxieties. “Weirdo nobodies,” was how one military historian characterized them to me. “They’re probably the least qualified group of foreign policy and national security advisers I’ve ever seen or even heard of,” said Richard Kohn, an expert in civil-military relations and retired professor at the University of North Carolina. A source with firsthand knowledge told me that Trump’s campaign pursued retired General David Petraeus, Middle East scholar Daniel Pipes and former U.N. Ambassador John Bolton, but all three men declined. In a TV appearance not long afterward, Trump said he wouldn’t hesitate to replace the members of his military team if they didn’t agree with him. (Trump’s campaign didn’t respond to multiple requests for comment.)

For even the savviest of presidents, the relationship between a commander in chief and his military is famously fraught, an intricate dance of egos and agendas, worldviews and bureaucracies. A President Trump, however, could usher in a clash of historic proportions. “If you take the man at his word,” said Michael Breen, the president of the Truman National Security Project and a decorated former Army officer, “we have a presidential candidate who seems to have committed himself to triggering what would probably be the greatest crisis in civil-military relations since the American Civil War.”