‘ And all the cities of those kings, and all the kings of them did Joshua take, and he smote them with the edge of the sword, and he utterly destroyed them, as Moses the servant of YHWH commanded.'
He also took the other cities that had taken part in the alliance, killed their kings (whether captured before or then) and slaughtered the people. This was in accordance with the command of God through Moses. None of the Canaanites were to remain alive lest they lead Israel astray after idols and into the gross immorality of their sexually perverted religion.