Some Biblical critics point out that Joshua’s campaign against the Canaanite people was ruthless and inhumane, often pointing to Israeli psychologist’s, Dr. Georges Tamarin, 1966 study of Joshua’s war tactics, which study involved the opinions of over a thousand Israeli children. They often point out Joshua 6:21and 8:25 as particularly disconcerting. Imagine, completely destroying Jericho and Ai and everyone within both cities, whether men or women, young or old. How can one justify this kind of warfare?
I’ll quote the verses here:
Joshua 6:21 And they utterly destroyed all that was in the city, both man and woman, young and old, and ox, and sheep, and ass, with the edge of the sword.
Joshua 8:25 And so it was, that all that fell that day, both of men and women, were twelve thousand, even all the men of Ai. (emphasis mine in both citations)
Something overlooked by the cursory reader is that these cities were not great population centers, but were actually fortresses populated by military and government personnel. Non-combatants, including women and children, lived in the surrounding regions. What would have taken place here would have been similar to what had already occurred during Israel’s wilderness campaign against Sihon, king of the Amorites (Numbers 21:21-32). There Israel fought the military who came out against them in battle, but drove out the non-combatants and dwelt in their cities.
Another point often brought up by the Biblical critic is how Joshua treated the bodies of the five kings he defeated (Joshua 10:24-27). As I have said previously, Israel was not the most righteous people in the ANE. They were no more righteous than the Egyptians whom God had judged on Israel’s behalf. What was important was that Israel received God as their God. This ended, technically if not practically, their rebellion against the God of the Bible. As the covenant-God, he was able to teach Israel better behavior, but this came about in increments throughout their history (and as they were receptive) not as a sudden cleansing at Mount Sinai. What Joshua did to the Canaanite kings was nothing worse than these same ANE nations were already doing to those they conquered (cf. 1Samuel 31:8-10).
Additionally, some of Joshua’s battles were defensive in nature. For example, Amalek first attacked Israel’s week and feeble who straggled behind unable keep up with the main body after leaving Egypt (Deuteronomy 25:17-18). Soon afterward they attacked Israel as they searched for water at Rephidim (Exodus 17:8). On another occasion Israel was attacked by the king of Arad (Numbers 21:1), and when king Sihon was approached by Israel to allow passage through his land via the Kings’ Highway, he flatly refused and went out to meet Israel in battle (Numbers 21:21-32). Not long after this, the king of Bashan came out against Israel (Numbers 21:33). Moreover, the king of Moab hired Balaam, a famous prophet of Mesopotamia, to curse Israel. When he couldn’t do that, he taught him and the Midianites how to seduce Israel into betraying their covenant with God (Numbers 31:1-3, 16). Finally, the five kings Joshua attacked in Joshua 10 was in defense of Gibeon with whom Israel had a peace treaty. Those kings attacked Gibeon, forcing Joshua to come to Gibeon’s defense.
As a whole, Israel, during Joshua’s campaigns against other ANE nations, often behaved better than their adversaries. We are never led to believe that Israel’s behavior was sub-standard or more cruel than the ANE cultures at that time. Rather, by giving Israel the Law as their constitutional code, God began to change Israel’s behavior for the better. Hard hearts (cf. Matthew 19:8) were a problem, but little by little and in increments throughout her history, Israel changed for the better, and that change began under Moses and Joshua.
 As I said HERE, this current theme about “making sense of the Old Testament God” is based upon the book: Is God a Moral Monster by Paul Copan. These are my thoughts about his book. He may or may not agree with the impression his book has made upon me, but I thoroughly enjoyed reading what Paul wrote and recommend his book to anyone who is looking for a good read concerning defending our faith.