(1) וקראת אליה לשלום, “you shall first offer peace to that city. According to some sages the rule mentioned here even included nations who the Israelites had been ordered by G–d to kill every “soul.” However, this command did not apply if the inhabitants agreed to vacate the town and relocate outside the Holy Land. We know that peace is superior to war, i.e. hostility, from when G–d Himself changed what Sarah had thought about her husband when she considered him too old to impregnate her with effective sperm. (Genesis18,12) He did not tell him about that part of her reaction to the angel’s prediction that by the following year she would have a son.... Both the blessings by the priests end with bestowing the blessing of peace and the last of the 19 benedictions in the amidah prayer that we recite at least three times daily, concludes with the blessing of shalom, peace. Our sages in the Talmud (Gittin 61) bid us to greet a gentile with the blessing of shalom before waiting for him to greet us, and in the event that he does to respond with using the expression shalom twice. Seeing that this might appear insincere on our part, the Talmud urges us to greet him before he can greet us so that we can avoid using the word shalom twice when greeting him, something that is forbidden in the Talmud (Gittin 62).
(1) כי תקרב אל עיר להלחם עליה וקראת אליה לשלום, “when you approach a city against which you are planning to make war, you shall (first) call to the city to (surrender) peacefully.” In this instance the Torah speaks about a war which, though it has been sanctioned by G’d via instructions given to the High Priest, is not an obligatory war. The standard name for such a war is milchemet reishut מלחמת רשות. In such wars, peaceful surrender is offered first. When confronting the seven nations residing in Canaan, which the Israelites were under orders to conquer, no such peaceful surrender is offered first (compare Rashi).
The fact is that the Torah does not spell out here whether a מלחמת רשות or a מלחמת מצוה is referred to in our paragraph. I am certain that any city in any war is included in this legislation, that peaceful surrender must be offered first with the exception of the wars against Ammon and Moav, concerning whom the Torah specifically wrote that “you must not seek their peace or their welfare” (Deut. 23.7). If, however, Ammon or Moav to whom no peaceful overtures are to be made by the Israelites volunteer peace, such overtures are accepted (Maimonides Hilchot Melachim 6,6). All of this teaches how powerful an objective peace is.