Joshua 10:5

‘ Therefore the five kings of the Amorites, the king of Jerusalem, the king of Hebron, the king of Yarmuth, the king of Lachish, the king of Eglon, gathered themselves together, and went up, they and all their hosts, and encamped against Gibeon, and made war against it.'

The five kings of the five city states gathered their combined forces for the purpose either of bringing Gibeon back into the Canaanite fold, or of punishing them severely for their treachery against their neighbours. It was an alliance forced on them by circumstances, each recognising that it was not powerful enough to face up to Gibeon and Israel on its own.

“Five kings of the Amorites.” The term ‘Amorites' was often used as a general name for the dwellers in the hill country (and sometimes for all of Canaan), although Jerusalem was in fact inhabited by Jebusites. These kings went with their fighting men and besieged Gibeon.