Joshua - Chapter 12
Role Call
The Navi now gives a list of kings defeated by Israel. First it lists those defeated by Moshe on the other side of the Jordan: Sichon and Og. Then it lists those conquered by Joshua, totaling thirty-one.
The Navi lists the thirty-one kings in an odd, apparently redundant, fashion. It says, "The king of Jericho, one; the king of Ai...one," etc. We could just count the kings and see there are thirty-one, without saying "one" after each king. The Radak says that each of these 31 kings ruled more than just the one city; the cities named were the capitals of their kingdoms.
While the thirty-one kings listed in this chapter were all destroyed, not all of their cities were necessarily occupied by Israel at this time. For example, Jerusalem would not be conquered until after the death of Joshua, in the first chapter of the Book of Judges (Shoftim).