Deuteronomy 20:10 - Matthew Poole's English Annotations on the Holy Bible

This seems to be understood not of the cities of the Canaanites, as is manifest from Deuteronomy 20:16-18, who were under an absolute sentence of utter destruction, Exodus 23:32,33 Deu 7:1,2; whence they are blamed that made any league or peace with them, Judges 2:2; but of the cities either of other nations who injured or disturbed them, or commenced war against them, or aided their enemies, or oppressed their friends and allies; or of the Hebrews themselves, if they were guilty or abettors of idolatry or apostacy from God, or of sedition or rebellion against authority, or of giving protection and defence to capital offenders. See Ge 15 Jud 20 2Sa 20, &c.