This verse says that Ai was never again occupied after it was destroyed by Joshua. But Nehemiah
(7:32) lists it among the cities of Israel at the time of the Babylonian captivity.
God promises to give Joshua all of the land that his "foot shall tread upon." He says that none of the people he
encounters will be able to resist him. But later we find that God didn't keep his promise, and that many tribes withstood
Joshua's attempt to steal their land. 1:3-5, 3:10, 15:63,
16:10, 17:12-13, 17:17-18, 21:43-45