President Donald Trump on Wednesday issued a hawkish threat to Mexican law enforcement personnel and drug traffickers, warning them he is sending “ARMED SOLDIERS” to the U.S.-Mexico border.

Trump appears to have been agitated by special counsel Robert S. Mueller’s depiction of his White House as a dysfunctional place where top aides defy his orders. Political analysts from both parties have noted when Trump feels in political or legal hot water, he typically returns to an immigration-based message.

That issue, perhaps more than any other, revs up the conservative base he will need to again turn out in big numbers to secure a second term.

The commander in chief alleged in a tweet that “Mexico’s Soldiers recently pulled guns on our National Guard Soldiers, probably as a diversionary tactic for drug smugglers on the Border.”

Then came a warning: “Better not happen again! We are now sending ARMED SOLDIERS to the Border.”

Mexico’s Soldiers recently pulled guns on our National Guard Soldiers, probably as a diversionary tactic for drug smugglers on the Border. Better not happen again! We are now sending ARMED SOLDIERS to the Border. Mexico is not doing nearly enough in apprehending & returning!

— Donald J. Trump (@realDonaldTrump) April 24, 2019

The exact meaning of the tweet was unclear. That is because U.S. military personnel are typically armed. His tweet could signal a shift in the rules of engagement, meaning they have clearance to use lethal force on U.S. soil, which could present legal challenges since they are being deployed for what technically is a domestic law enforcement mission.

Trump has already sent about 4,700 active and reserve troops to the southern border, according to Army Times, citing figures from senior Army leaders.

The president could also be trying to distract reporters from the Mueller report and its many damning findings about his White House and actions before and since taking office. Mueller found evidence he obstructed justice, for instance.

He is scheduled to leave the White House for a prescription drug speech in Atlanta around 10:40 a.m., and could be hoping reporters ask him about the border situation rather than the special counsel’s report.

In reality, however, he is likely to get questions on both subjects.

He recently said Mexican leaders had provided more assistance stopping Central American migrants from approaching the U.S. boundary — so much so that it was a major part of his decision to shelve his threat to close legal ports of entry despite warnings of an economic hit.

But on Wednesday, he returned to criticizing America’s southern neighbor: “Mexico is not doing nearly enough in apprehending & returning!”