The unannounced visit in Iraq followed in the footsteps of two of Trump's predecessors, Republican George W. Bush and Democrat Barack Obama, who both made surprise trips to see troops.
For security reasons, the visits are usually kept secret until after the president arrives. A small group of aides and Secret Service agents, and a pool of reporters, were with Trump and the first lady on the overnight flight from Washington.
Trump said his main security concern was for the first lady.
While in Iraq, Trump also spoke to military commanders and the U.S. ambassador. Sanders said they "came up with a powerful plan that will allow us to continue our path to total victory" over Islamic State.
Unlike Syria, Trump said he had no plans to withdraw from Iraq.
Trump has had an uneven relationship with America's military. He did not have to serve during the Vietnam War after being diagnosed with bone spurs in his heels.
As president-elect, Trump was drawn to the brawn of the armed forces and stacked his first Cabinet with generals, many of whom have since left his administration.
Trump has also wanted to end protracted U.S. involvement in overseas conflicts, and to force allies to pay more of the costs that he says fall disproportionately on American taxpayers, a point he made again on Wednesday.
Trump spoke to troops gathered in a dining hall festooned with holiday decorations and teased soldiers about their favorite football teams.
To reporters, he lamented the wear and tear of overseas conflicts.
“It's time to get our young people out," Trump said. "And I’ve been signing plenty of letters and I don’t like sending those letters home to parents saying that your young man or your young woman has been killed.
“I don’t like doing it. We’ve been doing it long enough.”
Trump also defended his decision to withdraw U.S. troops from Syria and said, "A lot of people are going to come around to my way of thinking."
Trump said he had told his advisers "let's get out of Syria," but was then persuaded to stay, before deciding to bring the 2,000 troops home.
"It's time for us to start using our head," the president told reporters at the Al Asad Air Base west of Baghdad where he and first lady Melania Trump spent three hours on the ground visiting U.S. troops.
