It’s the totally unthinkable question that Americans find themselves confronting this week: What would President Donald Trump do in a genuine national crisis?

After a series of overseas terror attacks and some startling statements about nuclear weapons and torture, the world’s attention has turned to Trump’s foreign policy—an area where he has few advisers, no experience and a tendency to fire off answers and deal with the fallout later. The reality of a Trump candidacy has begun to set in: If Trump is elected and a major national crisis hits, he’ll be the one with his hands on the button. He’ll be at the head of the table in the Situation Room. His decisions would steer America’s immediate response and could set the course of American policy for years.

What’s hard to project with a normal politician is nearly impossible to guess with Trump. He has no foreign policy or public service experience, which means there’s no official record to consult, and his public statements, while extreme, have been vague. The saber-rattling statements that excite his supporters also suggest he has disregard for linchpins of the global order like NATO, the Geneva Conventions and the hard-won global nuclear-weapons limits.