WASHINGTON — He canceled a trip to a cemetery in France where American soldiers from World War I are buried. He did not go to the observance at Arlington National Cemetery on Veterans Day. He has not visited American troops in Iraq or Afghanistan.

And shortly after becoming commander in chief, President Trump asked so few questions in a briefing at MacDill Air Force Base in Tampa, Fla., that top military commanders cut the number of prepared PowerPoint slides to three — they had initially planned 18 — said two officials with knowledge of the visit.

The commanders had slotted two hours for the meeting, but it lasted less than one.

Rhetorically, Mr. Trump has embraced the United States’ 1.3 million active-duty troops as “my military” and “my generals” and has posted on Twitter that under his leadership, the American armed forces will be “the finest that our Country has ever had.” But top Defense Department officials say that Mr. Trump has not fully grasped the role of the troops he commands, nor the responsibility that he has to lead them and protect them from politics.

“There was the belief that over time, he would better understand, but I don’t know that that’s the case,” said Col. David Lapan, a retired Marine who served in the Trump administration in 2017 as a spokesman for the Department of Homeland Security. “I don’t think that he understands the proper use and role of the military and what we can, and can’t, do.”