hors de combat (not non-combattants!) - translating the French borrowing will inevitably entail the loss of expressivity.

NYT about Ukrainian hors de combat

Moscow and Kyiv has each accused the other of committing war crimes in the same episode — the Russians accusing Ukraine’s forces of “mercilessly shooting unarmed Russian P.O.W.s,” and Ukraine’s commissioner for human rights, Dmytro Lubinets, saying Russian soldiers had opened fire during the act of surrendering.

“We are aware of the videos, and we are looking into them,” Marta Hurtado, a spokeswoman for the U.N. Human Rights Office, told Reuters on Friday. “Allegations of summary executions of people hors de combat should be promptly, fully and effectively investigated, and any perpetrators held to account.” Under international law, the French term “hors de combat” refers to people who are “outside of combat” because of their surrender, being unarmed, unconscious or otherwise unable to defend themselves.