Temps in Kabul, Afghanistan, during the same period are forecast to be in the mid-4 0s . There, more than 8,000 soldiers from the United States and more than three dozen allied countries are fighting against a resurgent Taliban after 17 years of war. Little wonder that the mission and the morale of those charged with achieving it are both being seriously questioned.

The forecast is rosier for the border with Mexico, where several thousand soldiers will have to spend the holidays away from their families, having been deployed there in a pre-election ploy by the president to rile up anti-immigrant sentiment.

He probably won’t have to worry about rain, which was the excuse given by the White House for his decision not to visit an American military cemetery in France while he was in Paris last month to commemorate the end of World War I.

There have been numerous and conflicting explanations for why Mr. Trump has avoided visiting troops downrange — he doesn’t agree with all the conflicts and doesn’t want to be associated with them, he’s too busy, he’s scared for his safety. Never mind that nearly every president since Dwight Eisenhower has safely visited soldiers in conflict zones from Vietnam and Korea to Iraq and Afghanistan. Barack Obama, for one, visited Iraq as a senator in 2008 and returned within his first three months in the White House. He went to Afghanistan four times.

What Mr. Trump’s excuses all reveal, however, is a basic misunderstanding. Visiting soldiers and sailors and Marines in the field isn’t about the president. It is about the troops. It’s about those who are close to the enemy and far from home, following orders and serving a cause greater than themselves.