Canaan was being given over to Israel, whom God had now brought out of Egypt. If the Canaanite tribes, seeing the armies of Israel, had simply chosen to flee, no one would have been killed at all. There was no command to pursue and hunt down the Canaanite peoples.
It is therefore completely misleading to characterise God's command to Israel as a command to commit genocide. Rather it was first and foremost a command to drive the tribes out of the land and to occupy it. Only those who remained behind were to be utterly exterminated. No one had to die in this whole affair

Subject: The Slaughter of the Canaanites Re-visited. Reasonable Faith. Retrieved on 2011-10-20., quoted in Dawkins, Richard (2011-10-20). "Why I refuse to debate with William Lane Craig". Guardian. Retrieved on 2011-10-20.