Deuteronomy 2:34 (ESV)

34 And we captured all his cities at that time and devoted to destruction every city, men, women, and children. We left no survivors.

As the first instance in Deuteronomy of ḥerem, Israel devoted to destruction the cities and their inhabitants. Holy war was conducted here since this part of the Transjordan had been designated as part of the Promised Land. Whatever is not holy cannot come into the presence of the Lord.