So much for the generals.

H.R. McMaster is out as White House national security advisor. Chief of Staff John Kelly is reportedly weakened. Here come John Bolton as NSA and Mike Pompeo as secretary of state to lead America's national security establishment. The possibility of America embroiling itself in a major war seems greater now than at any moment since the early years of George W. Bush.

These are scary times. So what the heck happened?

The answer: President Trump's masters of war turned out to be insufficiently belligerent. He fancies himself a brawler, wants to surround himself with other brawlers, and the restraint shown by the old generals in questions of politics and policy finally broke his limited patience.

Out with the negotiators. In with the the guys who want to fight. And if the new guys don't have as much experience with actually fighting? No problem: At least they talk tough on Fox News.

It has seemed like we might avoid this moment. When Trump entered the Oval Office a year ago, he surrounded himself with a Cabinet of manly men — guys, like Rex Tillerson, straight out of "central casting," yes, but also a number of former military officers who could buttress Trump's own sense of himself as a bruiser.

Trump's penchant for hiring generals — Kelly and Jim Mattis, the defense secretary, were both retired Marines while McMaster was still on active duty in the Army — raised concerns he might be erasing America's long tradition of civilian control over the military, but most folks were happy that there seemed to be a few restrained grownups in a West Wing otherwise populated by hangers-on and wannabe alt-right revolutionaries.

Here's the thing with a lot of military men, though: Throw them into the fight, and they'll give you everything they've got. But — having seen up close the human cost of war — they're often a little more cautious about starting a fight in the first place.

It's been this way for much of the post-Cold War era. As a general, Colin Powell famously resisted efforts to use the American military to solve problems that might best be addressed through other means: More than one news article from his heyday described him as a "reluctant warrior." It was frustrating as hell to the civilians who served with him: Madeline Albright reportedly complained, "What's the point of having this superb military you're always talking about if we can't use it?"

It's not hard to imagine Trump himself speaking those words, is it?

The president fancies himself a fighting man. This week, he tweeted out fantasies of bloodying Joe Biden; it's only been a few weeks since he suggested he would've confronted the Parkland shooter even without a gun. He talks about executing drug lords, throwing military parades, and turning the cops loose on criminals: The man did a stint in professional wrestling, for God's sake. If the Republican Party ever really believed in speaking softly and carrying a big stick, those days are gone. Today's GOP president believes in loudly letting everybody know about the size of his stick.

Trump's early personnel choices demonstrated a preference for belligerence over smarts. Michael Flynn, his first (short-lived) national security advisor, had been fired by the Obama administration, but talked a good game about fighting Islamic terrorists. Mattis has been more competent, but probably owes his job to two things: His "Mad Dog" nickname, and a particularly nasty quote from his time in Iraq.

McMaster, meanwhile, authored a book about the need for officers to give presidents their honest opinions. Kelly got a reputation for restraining Trump's worst instincts. Neither man is perfect, but neither did they stand a chance of remaining in his favor.

So now we have Bolton, who never met a war he didn't like, and Pompeo, who has thrilled to the idea of civilizational conflict with Islam. (Pompeo graduated first in his class from West Point, but spent more time in the business world than as a soldier.) The Obama administration's nuclear deal with Iran might soon end; so might peace on the Korean peninsula.

The problem with Trump's pugnaciousness? He's never had to face consequences for it. There have always been bone spurs, or security guys, or the fact that professional wrestling isn't real. As far as we know, he's never started a fight and gotten his nose bloodied for the trouble. Anybody who has experienced that lesson never forgets it. It's best not learned on the international stage.

In the absence of a good bar fight to settle the matter, Trump will keep fancying himself a brawler. He'll surround himself with men who encourage that notion. And we'll move inexorably toward a time when the spilled blood is all too real.