On the plus side, we get to say, “That’s why Trump won,” to countless day-to-day annoyances. Another celebrity “Dear Congress” video? T.W.T.W. Another Michael Gerson column? T.W.T.W. Apple eliminating the headphone jack? T.W.T.W. On the minus side, we get to fear imminent death. And that, as we watch Donald Trump take office, is the subject of this column.

Forget Russian hacking, Jeff Sessions, Betsy DeVos, judicial nominees, or presidential trash talk about CNN or flag burners. Barring major external events, life in the United States will change less dramatically than Trump’s biggest enemies think—of this I feel confident enough to bet real money. (Contact me and we’ll work out the details. Kindly avoid invective.) The trouble is there’s no barring external events. (I guess the bet is off.) Presidents come to office hoping to spruce up the ship and then realize how much time must be spent to keep it from foundering in a giant, hostile sea. Avoiding disaster—in the form of war—is the big challenge. That Donald Trump will fail to meet this challenge is the big fear.

War is the horrible wild card of presidencies. A prolonged stalemate in Korea left Harry S. Truman deeply unpopular by 1952, and he abandoned efforts to get re-elected. Vietnam not only cost Lyndon Johnson his presidency but also, because of the many lies that were told, destroyed the trust most Americans had in their government before then. And, no, I’m not forgetting Iraq. If the last 42 months of the presidency of George W. Bush had gone like his first 6 months, we’d merely have had kooky fiscal policies, poorly enforced borders, and a financial meltdown. Not ideal but not irremediable. Unfortunately, after September 11, 2001, a major security failure in itself, we saw ill-considered wars, a massive loss of blood and treasure, vast erosions of civil liberties, and even the use of torture on detainees in our custody. All that will keep hurting for decades to come.

Even presidents who try to scale things back find themselves drawn into more than they planned for. Barack Obama claimed to reject the Beltway playbook yet got us involved in overthrowing Muammar Qaddafi and funneling aid to rebels in Syria. Such efforts did the first Obama White House little good and left the next one with trouble it was ill-equipped to handle. Last year, the United States dropped more than 26,000 bombs in seven countries—what Obama’s critics call “America in retreat.” I’d hate to see an advance.

Several people in Trump’s circle seem to be eager to pursue conflict with Iran. That could cost countless American and Iranian lives and wreck his presidency fast. But that possibility is merely scary. Like other conflicts since the Second World War (with the exception of the attacks of 9/11), it would take place far from our shores. If we ramp up tensions enough with China or Russia, however, the war could come to us. That’s what’s truly terrifying about Trump—the possibility, not high (but higher than normal), that life as we know it will end. Trump would never deliberately court such an outcome, but he seems likelier than any president we’ve ever had to blunder into it.

Little fear of Trump’s foreign policy has to do with his overall assessments of the world stage—including the strategic value of joining forces with Russia against ISIS—many of which could be sound, in theory. But everything in foreign affairs is about how others interpret what you’re saying or doing on a deeper level. People still debate whether Saddam Hussein felt he’d gotten a green light to invade Kuwait from ambiguous statements made by U.S. ambassador April Glaspie, but they didn’t help. Similarly, most people agree that the decision by Jimmy Carter to admit the recently deposed shah of Iran for treatment in the United States in 1979 came across to Iranian revolutionaries as proof of conspiracy and led them to invade the U.S. embassy in Tehran and take its staff hostage. Given Trump’s habit of tweeting before thinking, we could get a couple of Glaspies and shahs a day.