But if they refuse to make peace with you and wage war against you, lay siege to that city.
12. And if he will make no peace. The permission here given seems to confer too great a license; for, since heathen writers “Et cum iis, quos vi deviceris, consulendum est; tum 2, qui, armis positis, ad imperatorum fidem confugient, quamvis murum aries percusserit, recipiendi sunt.” — Cic, de Off. 1:11.
They are here directed what method to take in dealing with the cities (these only are mentioned, Deu 20:10, but doubtless the armies in the field, and the nations they had occasion to deal with, are likewise intended) upon which they made war.
Commenting on Deuteronomy 20:10-20
And if it will make no peace with thee,.... Will not accept of terms of peace offered: but will make war against thee; come out and fight, or prepare to defend themselves: then thou shall besiege it; surround and block it up on all sides with their forces; the Jews say only on three sides, leaving one for any to flee and make their escape...