Dear friends, as promised, this is the essay i talked about. Hope it helps you in understanding the Old Testament.

The Conquest and the Ethical Question of War

Many readers of Joshua (and other OT books) are deeply troubled by the role that warfare plays in this account of God’s dealings with his people. Not a few relieve their ethical scruples by ascribing the author’s perspective to a pre-Christian (and sub-Christian) stage of moral development that the Christian, in the light of Christ’s teaching, must repudiate and transcend. Hence the main thread of the narrative line of Joshua is an offense to them.

It must be remembered, however, that the book of Joshua does not address itself to the abstract ethical question of war as a means for gaining human ends. It can only be understood in the context of the history of redemption unfolding in the Pentateuch, with its interplay of divine grace and judgment. Of that story it is the direct continuation.

Joshua is not an epic account of Israel’s heroic generation or the story of Israel’s conquest of Canaan with the aid of her national deity. It is rather the story of how God, to whom the whole world belongs, at one stage in the history of redemption reconquered a portion of the earth from the powers of this world that had claimed it for themselves, defending their claims by force of arms and reliance on their false gods. It tells how God commissioned his people to serve as his army under the leadership of his servant Joshua, to take Canaan in his name out of the hands of the idolatrous and dissolute Canaanites (whose measure of sin was now full; see Ge 15:16 and note). It further tells how he aided them in the enterprise and gave them conditional tenancy in his land in fulfillment of the ancient pledge he had made to Israel’s ancestors, Abraham, Isaac and Jacob.

Joshua is the story of the kingdom of God breaking into the world of nations at a time when national and political entities were viewed as the creation of the gods and living proofs of their power. Thus the Lord’s triumph over the Canaanites testified to the world that the God of Israel is the one true and living God, whose claim on the world is absolute. It was also a warning to the nations that the irresistible advance of the kingdom of God would ultimately disinherit all those who opposed it, giving place in the earth only to those who acknowledge and serve the Lord. At once an act of redemption and judgment, it gave notice of the outcome of history and anticipated the final destiny of humankind and the creation.

The battles for Canaan were therefore the Lord’s war, undertaken at a particular time in the program of redemption. God gave his people under Joshua no commission or license to conquer the world with the sword but a particular, limited mission. The conquered land itself would not become Israel’s national possession by right of conquest, but it belonged to the Lord. So the land had to be cleansed of all remnants of paganism. Its people and their wealth were not for Israel to seize as the booty of war from which to enrich themselves (as Achan tried to do, ch. 7) but were placed under God’s ban (were to be devoted to God to dispense with as he pleased). On that land Israel was to establish a commonwealth faithful to the righteous rule of God and thus be a witness (and a blessing) to the nations. If Israel became unfaithful and conformed to Canaanite culture and practice, it would in turn lose its place in the Lord’s land—as Israel almost did in the days of the judges, and as it eventually did in the exile.

War is a terrible curse that the human race brings on itself as it seeks to possess the earth by its own unrighteous ways. But it pales before the curse that awaits all those who do not heed God’s testimony to himself or his warnings—those who oppose the rule of God and reject his offer of grace. The God of the second Joshua (Jesus) is the God of the first Joshua also. Although now for a time he reaches out to the whole world with the gospel (and commissions his people urgently to carry his offer of peace to all nations), the sword of his judgment waits in the wings—and his second Joshua will wield it (Rev 19:11–16).

NIV Study Bible by Zondervan.