The conquest of Canaan in the Book of Joshua was supposed to be the sequel to the exodus: an oppressed people, now liberated, overcome insurmountable odds to make a home for themselves in a hostile country. Today, however, many criticize the book as a blueprint for genocide. Still more troubling, some people in history have actually taken the book as a model for carrying out holy war. (The slaughter of the Canaanites never set well with most non-Israelites, however; in the first century, some Jewish writers with audiences outside the holy land avoided the topic or transformed its focus.)
How we read and apply the book, then, makes a life-and-death difference. In reading it, however, several factors should be taken into account. The most important factor for Christians I reserve for the end (in part III).
First, Old Testament scholars now emphasize the genre of Joshua’s conquest accounts. Ancient conquest lists functioned as triumph boasts, but they were understood to communicate only part of a story. Thus Egyptian records could say, “We subdued these cities”—and Egypt’s army had to march into those cities the next spring for a new offensive. Sometimes they declared, we “utterly annihilated” peoples, but the peoples continued to exist; the boast simply means they defeated their warriors. Likewise the Israelites sometimes defeated enemies “completely”—and then some of the enemies escaped (Joshua 10:20). As in some other ancient conquest lists, Israel reportedly took all the land (Joshua 10:40; 11:11, 16, 19)—yet much land in fact remained to be taken (13:1-7). Only a minority of cities were actually destroyed (Joshua 11:13), cities defeated at one point often had to be retaken (cf. Joshua 8:17, 22, 24; 12:16; Judges 1:22-25), and Israel settled mostly in the hill country. Both the Book of Judges and archaeological evidence (if we have in view the right period) show us that Joshua’s conquest lists, like others of the era, summarized victories in glowing terms not always intended completely literally.
Second, God did not allow Israel to take the land until “the sin of the Amorites” living there “has … reached its full measure” (Genesis 15:16, New International Version). That is, God was executing judgment on the Canaanites through the invasion. If God could destroy most of humanity in a flood or could destroy Sodom and Gomorrah through fire, he could also send judgment through other means that he chose, including invasions. For example, God later judged Israel and Judah through Assyria and Babylon, although the agents of his judgment intended the violence only for their own purposes and would in turn be judged for their sin (Isaiah 10:5-14).
Whether we like it or not, God has the right to judge humanity; whether we like it or not, every one of us will sooner or later face death in one way or another, and must answer to him for our choices. Once Canaan’s sin “reached its full measure,” God had the right to execute capital punishment on the society, and chose to do it through Israel. This is why God’s orders clearly restricted this punishment to the land in question. “Holy war” and devoting things to deities for destruction were concepts understood in cultures surrounding Israel. But Israel could fight such a war only under God’s direct orders (though we also see a “just war” in Gen 14:14-16 to free slaves; cf. 2 Samuel 30:7-8, 18-20).
Third, God knew what would happen to Israel if they shared the land with the Canaanites—what did in fact happen later. At this time Israel was virtually alone among surrounding cultures in being monotheistic and aniconic (no deity-images). Israel would be very susceptible to “progressive” outside influences from apparently stronger cultures. Based on thousands of remains of cremated babies at Carthage (a Phoenician settlement elsewhere) and other evidence many scholars speak of Canaan’s special depravity. Many Canaanite towns’ annual revolts against Egypt, once Egyptian armies were no longer in sight, also suggest that nothing less than total war would subdue them firmly.
Fourth, most of the peoples in the land chose to fight Israel, ensuring these peoples’ destruction (Joshua 11:20). Pacifism has much to be said for it as an expression of sacrificial Christian devotion, but ancient Israel did not yet have the foundations for such an approach. Had Israel sought to settle in the land without fighting, their enemies would have annihilated them. God does perform miracles, but often through what is already at hand (e.g., Exodus 14:21); in this case, God promised Israel victory but also summoned them to do their part and fight for it.
Nevertheless, if there is any continuity at all in the biblical picture of God, the slaughter of the Canaanites cannot ever have been God’s ideal.(One may also consult works such as a recent book by Paul Copan: http://www.amazon.com/Is-God-Moral-Monster-Testament/dp/0801072751)