President Trump demands loyalty from everyone around him. And his method of obtaining it is often unorthodox: by forcing people to sign off on — or even vouch for — his most controversial and nonsensical ideas. The people in his orbit almost always do, to one extent or another, because the alternative is undercutting the president of the United States. Once they’ve bought in, their fate is more tied to his.

Defense Secretary Jim Mattis has to this point largely avoided such an arrangement. Speaking in public infrequently, he has earned a reputation as a bipartisan, steadying force within the administration. And with Nikki Haley’s impending exit as U.S. ambassador to the United Nations, he’s set to be the most popular and reputable Cabinet official left.

But Mattis’s tolerance is now being tested — as is his reputation.

Mattis earlier this week vouched for Trump’s decision to send 5,200 troops to the U.S.-Mexico border to contend with the caravan of migrants that started in Honduras. Critics have alleged it’s a thinly veiled electoral ploy in which the Pentagon is now complicit, but Mattis rejected that criticism in no uncertain terms.

“The support that we provide to the secretary for Homeland Security is practical support based on the request from the commissioner of customs and border police,” Mattis said. “So we don’t do stunts in this department.”

“We don’t do stunts in this department.” Translation: We’re not letting Trump use us for political gain.

Since Mattis uttered those words Wednesday, though, Trump has upped the ante even more. Just a couple of hours later, Trump floated the idea of sending as many as 15,000 military personnel to the border — a number that would far outstrip even the number of migrants in the caravan and would also rival the number of troops in Afghanistan.

Then, on Thursday, Trump suggested that those troops should respond to any rocks being thrown their way by shooting at the caravan. “If they want to throw rocks at our military, our military fights back,” Trump said. “We're going to consider — and I told them, consider it a rifle. When they throw rocks like they did at the Mexico military and police, I say, consider it a rifle.”

Trump’s suggestion isn’t serious. Even if the military wanted to respond to such provocations with deadly force and wasn’t worried about creating an international incident, it doesn’t broadly have the authority to engage in law enforcement — much less combat — on U.S. soil. Its role, legally speaking, is one of support for existing agents. It can’t technically do much the National Guard, which had previously been marked for deployment, couldn’t do.

That’s a big part of why this is viewed as a stunt — with the other main ones being that the military is being deployed with the caravan still 900 miles and weeks away, and also that such caravans generally are aimed at legally requesting asylum rather than crossing the border illegally. Trump’s rhetoric that this constitutes an “invasion” or that we have an immigration “crisis” simply isn’t backed up by the facts.

Trump’s overzealous rhetoric has made clear, at the least, that he is trying to leverage this for political gain. Whether the deployment of the military itself is an unwarranted piece of that effort is for reasonable people to disagree about.

But Mattis has now bought into the idea that it’s not. And Trump seems bent upon making him regret it.