Joshua 10:1, 2

Now Adoni-Zedek king of Jerusalem heard that Joshua had taken Ai and totally destroyed it, doing to Ai and its king as he had done to Jericho and its king, and that the people of Gibeon had made a treaty of peace with Israel and had become their allies.

He and his people were very much alarmed at this, because Gibeon was an important city, like one of the royal cities; it was larger than Ai, and all its men were good fighters.