In his campaign for a second term, President Trump promised that he would get and keep the United States out of wars. In his inaugural address, he said he wanted to leave a legacy of “unification.” And after just under eight months in office, he is openly campaigning for a Nobel Peace Prize.

But this week, Mr. Trump sent a conflicting message. The “President of Peace,” as the White House has branded him, signed an executive order to establish a “Department of War.”

The change speaks to the contradictions in Mr. Trump’s presidency and the image he projects to the world, on the one hand seeking the ultimate prize for peace while at the same time promoting a far more aggressive use of U.S. military might.

He even suggested in a social media post on Saturday morning that he would go to “war” with a city in his own country where he has threatened an immigration crackdown. He said Chicago was “about to find out why it’s called the Department of WAR,” along with three helicopter emojis.

Asked on Friday about how he squared his Department of War with his push for peace, Mr. Trump did not see a contradiction.

“I think I’ve gotten peace because of the fact that we’re strong,” he said. (Mr. Trump claims to have solved at least seven wars, a statement that requires context.)