Joshua and Judges present different versions of the Israelite conquest.
The following article is reprinted with permission from A Historical Atlas of the Jewish People edited by Eli Barnavi and published by Schocken Books.
The Books of Numbers and Deuteronomy recount how the Israelites captured territories east of the Jordan River which were later settled by the tribes of Reuben, Gad, and half of Manasseh. The Book of Joshua then presents the "official" biblical version of the conquest and settlement of the Promised Land. The people of Israel, assembled on the eastern banks of the Jordan, were ready to cross the river and conquer the land of Canaan.
Joshua son of Nun, Moses' successor, first sent spies and, encouraged by their report about the fear of the Canaanites, immediately decided to attack Jericho, the strongest town in the area. The miraculous fall of Jericho opened the road inland. Joshua led his people southward, then towards the hills of Judea, and later to the north, in a series of successful campaigns crowned by the conquest of Hazor--the strongest town in the north. The capture of Shechem is not mentioned, but the Bible states that once the conquest was completed, the people of Israel gathered there for a national assembly, an indication that Shechem was already in the hands of the tribes of Israel.
The historical validity of this account of the conquest is highly dubious. Analysis of other biblical texts reveals many discrepancies. The Book of Judges recounts separate campaigns by individual tribes; and, although it places the events after Joshua's death, they constitute in fact a different version of the story of the conquest. The Book of Joshua describes a well‑organized campaign of a people united by a common national goal, while the Book of Judges reports many separate battles against Canaanite peoples waged by individual tribes or by temporary alliances of several tribes, enlarging their territories at the expense of their neighbors.
Furthermore, according to the Book of Joshua, the entire country was taken by the Israelites, while the Book of Judges reveals that one of the severe problems of the tribes was the constant struggle with Canaanite enclaves which successfully retained their independence.
Finally, in the period covered by the Book of Judges, the tribes were headed by local commanders (the "judges"), and there was no single national leader. The editor of the Book of Judges regarded this as a sign of social disintegration following the death of Joshua--divine punishment for lapses of idolatry. Modern scholars, however, believe that the state of anarchy reflected in the Book of Judges is closer to the true historical process of the colonization of Canaan.