A nation has to know that military action being taken in its name follows morally defensible rules — that soldiers do not, for instance, kill unarmed civilians or prisoners.

To excuse men who have so flagrantly violated those rules — to treat them as heroes, even — is to cast the idea of just war to the winds. It puts the nation and veterans at risk of moral injury, the shattering of a moral compass.

One of the loudest groups pushing for Mr. Trump’s pardons was United American Patriots, a nonprofit organization that supports numerous soldiers accused of crimes, including Mr. Lorance, Mr. Behenna and Major Golsteyn. Last month, Chief Gallagher sued two of his former lawyers and United American Patriots, alleging that his lawyers tried to delay the case to increase fund-raising for the organization.

Supporters of the pardoned men say the military justice system comes down too hard and too often on honorable soldiers fighting through the fog of war. That wouldn’t explain why United American Patriots has made a cause célèbre of Robert Bales, who pleaded guilty to slaughtering 16 Afghan civilians in their homes during a one-man nighttime rampage in 2012.

The president might truly believe these pardons won’t endanger soldiers by damaging allied support or emboldening enemies, and they’re probably unlikely to encourage future war crimes, though critics have raised such a specter.

But the impact such formal absolution will have on the veterans of these murky wars and the society that they are working to rejoin will be lasting. Venerating these pardoned men will cause even greater damage.

Mr. Lorance was a lieutenant with three days of experience leading his platoon when the murders occurred. His men testified that one of the first things he told the platoon was that they should conduct night raids to terrorize civilians, even children. When one of his men told him that there were three men on a motorcycle about 200 yards away, he ordered his troops to shoot them.