Just before midnight Tuesday, President Trump departed the White House for his first visit to U.S. troops in a combat zone. Of course, it wasn’t just any Tuesday. It was Christmas. A president with his troops at Christmastime — look no further than George Washington crossing the Delaware on the night of Dec. 25, 1776, to understand the sentimental response this elicits in many Americans. Senior administration officials claim the trip had been in the works for weeks. One would be forgiven, however, for concluding that in the wake of the government shutdown, the resignation of Secretary of Defense Jim Mattis, and the controversial announcement of plans to withdraw troops fully from Syria and partly from Afghanistan, Trump decided that this was an opportune moment to harness the powerful iconography of a commander in chief over the holidays with the men and women who serve, particularly one who was there to deliver the message that many of their comrades in arms would soon be returning home. What better gift?

However welcome that message might be, it does not offer reassurance that peace is at hand, even if we tend to think so. Troops returning home doesn’t mean a war is over. On the contrary, a total withdrawal is more likely to mean that a war is lost than won. And it leaves the United States open to a more significant emergency deployment of troops later on.

If we look at a history of America’s wars, the conflicts we’ve won and crafted into a lasting peace have always required some of our troops to stay, from the Civil War and Reconstruction to the Second World War and subsequent European and Japanese occupations. Troops deployed need not be seen as troops at war — the notion that they are equivalent is harmful to creating an effective national security strategy. We can keep the troops deployed, thus securing our interests, while also keeping them relatively secure, as we’ve long done in places like Korea. President Barack Obama couldn’t see this possibility and made a mistake by pulling all the troops out of Iraq in 2011, only to have to redeploy thousands before the end of his administration after the Islamic State swept through the country. Trump is about to make the same mistake by pulling them all out of Syria and dangerously reducing them in Afghanistan.

Binary concepts of war and peace are inadequate to understanding the nature of U.S. military force projection abroad. Look at Germany, where we have 35,000 troops stationed, or at Japan, where we have 40,000 troops. Debates about “exit strategies” and “troop levels” are seldom used in those cases; there are no wars in those countries, but there are troops in them. The troops came home from Vietnam and interventions like Somalia — and those conflicts cannot be called victories. For a president who likes to “win,” Trump doesn’t seem fluent in what his orders to withdraw will mean.

The president argues that “the United States cannot continue to be the policeman of the world.” As someone who spent eight years fighting in these wars and who understands their costs firsthand, I’m certainly sympathetic to that logic. Trump is hardly the first person to make this case, one he equates with his “America First” brand of nationalism. However, his promise to “Make America Great Again” is contingent on an engaged foreign policy.

One might infer that the again in his slogan — stitched into the caps he signed for some of the troops on his Iraq visit — would include the Eisenhower and Reagan years, two presidents Trump openly admires. Both the 1950s and 1980s were decades of sustained American engagement abroad, from the implementation of the post-World War II Marshall Plan, which rebuilt and developed European markets for American goods, to Reagan’s Cold War engagement that led to perestroika, the dissolution of the Soviet Union, and the opening up of Eastern Europe and its markets. A capitalist like Trump should appreciate that American engagement has never been synonymous with American altruism alone.

Nevertheless, Trump is quick to dismiss the strategic imperative of sustained American influence in Syria, Afghanistan and Iraq, choosing instead to view them as regional problems. Trump has also played down the possibility that a vacuum of U.S. military power in Syria could allow the Islamic State to rebuild, despite an inspector general report from the Pentagon in summer estimating that more than 30,000 Islamic State fighters remain in Iraq and Syria.

“If we see something happening with ISIS that we don’t like,” Trump said, speaking Wednesday, “we can hit them so fast and so hard . . . they really won’t know what the hell happened,” adding that he has no plans to remove U.S. troops from Iraq. But without U.S. forces in Syria, the Islamic State will have a sanctuary from which to operate. Consider the current challenges along the Afghanistan-Pakistan border, or the flawed American strategy in Vietnam, which never dealt with enemy sanctuaries in Cambodia and Laos, to understand how crippling a sanctuary in Syria will be to security in neighboring Iraq.

During his Christmas visit to the al-Asad Air Base in Iraq, Trump explained how he had repeatedly directed “the generals” to get out of Syria, but they had continually asked for six-month extensions. “I said, ‘Nope. You can’t have any more time. You’ve had enough time. We’ve knocked them out,’ ” he said, referring to the Islamic State. “ ‘We’ve knocked them silly.’ ”

Trump, who once surrounded himself with generals, seemed unwilling to listen to any of them on this issue. Most are now gone from his administration — Michael Flynn, H.R. McMaster, John F. Kelly and now Mattis. If only one of them could have put the matter into terms he might have appreciated: Someone could have told the developer turned president about the Christmas holiday in 1944, when Gen. George S. Patton was fighting a desperate campaign against the German army in the Ardennes Forest, later known as the Battle of the Bulge. The fighting was about 50 miles west of Ramstein Air Base, where Trump stopped to refuel and hold a rally with troops on his way back from Iraq. When Patton’s exhausted Third Army was confronted with several days’ more fighting, one of his subordinates suggested they withdraw and regroup. As recounted in the 1970 movie “Patton,” the general says, “Not me,” and then adds, “I don’t like to pay for the same real estate twice.”