Opinion | I Served in the Army. Trump’s War Crimes Decisions Are Not Pro-Military.

The lessons service members learn about the laws of war are not an afterthought. Rather, they are central, emphasized time and again — from training sessions and exercises, to military ethics discussions, to actual combat deployments. The Army’s official values, after all, demand that soldiers “do what’s right, legally and morally” and “treat others with dignity and respect,” making no exceptions for civilians or even enemies.

The military requires its members to operate in accordance with the laws of war for good reason. Disregarding the laws of war — which Mr. Trump has done by intervening in these cases — jeopardizes mission accomplishment and the safety of service members; excessive civilian casualties, for example, can stimulate further violence, turn local populations against American forces, and discourage allies from collaborating with the United States. Mr. Trump should realize that the laws of war actually serve to benefit our armed forces.

Against this backdrop, Mr. Trump’s intervention on behalf of those convicted or accused of conduct falling short of the military’s crucial legal requirements and moral expectations undermines the training in which the military rightly invests so much effort. It trivializes the values the military spends so much time fostering. He could be endangering United States service members deployed to combat zones by handing their enemies propaganda and recruitment material and by degrading support among local populations.

To be sure, war is complex, and service members accordingly face difficult moral choices under extraordinary pressure. But their preparation helps them make sound decisions in these tough situations, and the military justice system considers the factual circumstances of each case and the intent of the actor.

Mr. Trump appears to be following in the unfortunate footsteps of President Richard Nixon. In the wake of Lt. William Calley’s murder conviction in connection with the Vietnam War’s My Lai Massacre, President Richard Nixon intervened on behalf of Mr. Calley. In a response to Mr. Nixon that rings true today, Capt. Aubrey Daniel, the military prosecutor in the case, wrote:

“Your intervention has, in my opinion, damaged the military judicial system. … I would expect that the president of the United States, a man whom I believed should and would provide the moral leadership for this nation, would stand fully behind the law of this land on a moral issue which is so clear and about which there can be no compromise.”

Mr. Trump, to the detriment of the United States Armed Forces, remains fixated on condoning the aberrant conduct of those convicted or accused of flouting the laws of war. He should have left the military justice system do its job. But perhaps this is not surprising, considering that Mr. Trump himself has recently advocated a war crime — the appropriation of oil in Syria.

Benjamin Haas served as an intelligence officer in the Army and was deployed to Afghanistan twice.

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