The Bible is emphatic in saying that God is not the author of death or of conflict, but rather these things come through sin, disobedience and rebellion (Rom. 5:12, 12:17-21,1 Cor. 14:33). God is the "God of peace" (Rom. 15:33, 16:20, Phil. 4:9).

Nevertheless, sin and death are in the world, and God deals with us as we are. There is a direct connection of course between war and sin (as in James 4:1 "What causes fights and quarrels among you? Don't they come from your desires that battle within you?" NIV). Nor do human wars have anything to do with or value for the kingdom of God.

John 18:36 Jesus said, "My kingdom is not of this world. If it were, my servants would fight to prevent my arrest by the Jews. But now my kingdom is from another place."

2 Cor 10:3 For though we live in the world, we do not wage war as the world does. 4 The weapons we fight with are not the weapons of the world. On the contrary, they have divine power to demolish strongholds. NIV

The kingdom of Israel of course was a kingdom in this world, with territory and borders and all that goes with that. God dealt with them in the circumstances in which they existed, and that included wars for various purposes. Still, there is a prespective of God in these matters that we don't necessarily share. For example, when God delivered Israel from Egypt and started them toward the land of Canaan (Exodus 1-14) he promised them the land of the Amorites (among others, Ex. 3:17) and promised to drive out the Amorites (and others, Ex. 34:11). One factor we shouldn't miss in this is that God had timing and conditions in mind that humans might not perceive. God had told Abraham more than four hundred years earlier, "In the fourth generation your descendants will come back here, for the sin of the Amorites has not yet reached its full measure." Genesis 15:16 NIV
So when Israel went into Canaan to displace the Amorites it was, as long before predicted by God, because the sin of the Amorites had reached full measure. There is a limit to how depraved any nation or culture can become before judgment by some means is necessary. Perhaps one way God forestalls the end of all things until the time of his choosing is punitive measures to forestall the earth being filled with violence as it was in the days of Noah.

The example Alena mentions of the Amalekites is another where judgment on the culture/nation had been pronounced in the days of Moses (Ex. 17:14) and about 400 years later Saul was instructed to carry out this judgment at the right time (1 Sam. 15:1-3). The judgment on the Amorites or on the Amalekites (or any other nation) might have been at least postponed or God might have relented had they responded as Ninevah did to the preaching of Jonah (Jonah 3:10). God does not have a vested interest in war, that is, he has not lusts to satisfy, no craving for territorial expansion or revenge, rather his use of war has always been as an instrument of judgment and as a prevention of even greater ills. He has the wisdom and foreknowledge that enable him to use war effectively for the best possible outcome.

It does seem to me that having an infinite perspective, God is able to make fair decisions about the need for war, as he did with Israel, that no man can make. He knows when the best possible thing is the annihilation of a culture, but none of us really do. He is able to sort out the "innocent" in an eternal sense, which is what matters ultimately (elsewhere in LivWat there is a discussion of how this was probably a factor in Noah's preaching to his world, not an invitation into the ark, but an invitation to reconcile with God and prepare for death).

With all that we can say to clarify God's use of Israel in war (certainly more can be said than this), it's important not to forget that war was not God's ideal, that sin and the need for limiting its effect brought it about, and tha