WASHINGTON — President Trump put thugs in crime-ridden Chicago on notice Saturday, promising to send in the newly-renamed Department of War in a threatening Truth Social post.

“Chicago about to find out why it’s called the Department of WAR,” the president wrote, referencing his Friday executive order renaming the Department of Defense to its original name.

The post was accompanied by an AI picture of Trump seated with fire and helicopters with the Chicago skyline in the background, dressed as the character Robert Duvall played in the movie “Apocalypse Now.”

Chicago Mayor Brandon Johnson also weighed in: “The President’s threats are beneath the honor of our nation, but the reality is that he wants to occupy our city and break our Constitution.”

“We must defend our democracy from this authoritarianism by protecting each other and protecting Chicago from Donald Trump,” Johnson wrote on X.

The president had first said he wanted to wait for Pritzker to voluntarily invite the troops, but raged in the Oval Office remarks that his patience was thinning.