John Calvin Commentary Deuteronomy 20:10

"When thou drawest nigh unto a city to fight against it, then proclaim peace unto it." — Deuteronomy 20:10 (ASV)

When thou goest forth to war. He now teaches that, even in lawful wars, cruelty is to be repressed, and bloodshed to be abstained from as much as possible. He therefore commands that, when they have come to take a city, they should first of all exhort its inhabitants to obtain peace by capitulating; and if they do so, to keep them alive, and to be content with imposing a tribute on them.

This principle of equity was naturally implanted in all nations; thus heralds arose,⁴⁵ nor did they commence a just war without a solemn proclamation. Besides, since the word hostis (an enemy) formerly signified a foreigner (peregrinum), the Romans, by its mildness, mitigated the sadness of the reality. For this reason, they deemed that faith was to be kept with an enemy; and that sentiment of Cicero is worthy of praise, “that wars must not be undertaken except that we may live in undisturbed peace.”

But if God wishes His people to be mindful of humanity in the very midst of the din of arms, we may therefore infer how greatly displeasing to Him is human bloodshed. Even those whom He has armed with His authority, He still wishes them to be disposed to clemency, and He represses their ardor, lest they stain with blood the swords given them by His permission. How, then, can it be lawful for a private person to assume the sword for the purpose of killing his brother? We now understand the purpose of the instructions here given, and how appropriately they are connected with the Sixth Commandment.

⁴⁵ “Feciales.” — Lat. “Les herauts d’armes.” — . “Les herauts d’armes.” — Fr. “The Romans never carried on any war without solemnly proclaiming it. This was done by a set of priests called . “The Romans never carried on any war without solemnly proclaiming it. This was done by a set of priests called Feciales. When the Romans thought themselves injured by any nation, they sent one or more of these . When the Romans thought themselves injured by any nation, they sent one or more of these Feciales to demand redress, (to demand redress, (ad res repetundas,) Liv. 4:30, 38:45. Varro, L.L. 4:15. Dionys. 2:72; and, if it was not immediately given, thirty-three days were granted to consider the matter, after which war might be justly declared. Then the. ,) Liv. 4:30, 38:45. Varro, L.L. 4:15. Dionys. 2:72; and, if it was not immediately given, thirty-three days were granted to consider the matter, after which war might be justly declared. Then the. Feciaks again went to their confines, and having thrown a bloody spear into them, formally declared war against that nation, Liv. 1:32.” — Adam’s Romans Antiq. again went to their confines, and having thrown a bloody spear into them, formally declared war against that nation, Liv. 1:32.” — Adam’s Romans Antiq.