Yes, the "Yeah, but he did it to!" and "What about them?" are grammar school defenses when caught breaking the rules. What I don't see are the rules. What ethical and moral wartime standards for the period are in play here?

Bill

Interesting you should ask.

Garrard Glenn, in The Army and the Law (1918) quoted (by Tom Holberg) re. Wellington’s advance into France, previously discusses military government and an army’s jurisdiction over civilian population. (pp.104-105)
https://archive.org/details/armyandlaw00glengoog/page/n116

Citing Napoleon in passing: “the laws of war confer on the Commander la grande police over the country which is the theatre of war,” he offers this U.S. Supreme Court dictum:
“[martial law is] the law which governs an army invading an enemy's country. It is not the civil law of the invaded country; it is not the civil law of the conquering country; it is military law — the law of war — and its supremacy for the protection of the officers and soldiers of the army, when in service in the field in the enemy's country, is as essential to the efficiency of the army as the supremacy of the civil law at home, and in time of peace, is essential to the preservation of liberty.”

He closes the with the Duke of Wellington: “Martial law is the will of the commanding officer of an armed force or of a geographical military department, expressed in time of war, within the limits of his military jurisdiction as necessity demands and prudence dictates, restrained or enlarged by the orders of his military or supreme executive chief.”