And if it will make no peace with thee, but will make war against thee, then thou shalt besiege it:
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...