Why do Black troops face a harsher form of military justice?

Cultural shifts in the U.S. military have often served as a bellwether for larger social change. By taking on racism in its criminal justice system, the Pentagon might reveal ways to address broader injustice.

Two years ago, the U.S. military decided to prosecute a Black service member for being six minutes late to a meeting, bringing his case to a court-martial hearing and, ultimately, a conviction.

“That’s a decision that truly should not have been made,” retired Col. Don Christensen, who previously served as the Air Force’s chief prosecutor, told...