By the time Joshua died, the Israelites had reached the promised land, and had  already conquered many parts of it.  Now it was time for the land to be divided among all the people.  The land was divided by tribe, meaning there was an area of land for the descendents of each of Israel's sons.  The descendants of Judah went to take possession of their land, and took the hill country.  But they were not able to drive the people from the plains, because those people had chariots of iron.