One of the most common and serious objections to Christian faith is that the Bible (especially the Old Testament) is ‘full’ of bloodshed that has been carried out in the name of, or even at the express command of, God.
I don’t want to offer glib answers to this objection. However, it may be useful to try to summarise, as briefly and as honestly as I can, what the Bible teaches about war.
1. War is repugnant to God, 1 Chron 22:8f; Psa 68:30; 120:6f; Isa 10:13ff; Amos 1:11, 13.
2. The Bible speaks in glowing terms of world-wide peace as the present ideal and future hope, Psa 46:9; Isa 2:4; 9:5-7; Mic 5:3; Zech 8:4ff; 9:10; Hos 2:18.
3. However, in the OT, many wars were allowed or even commanded, Ex 15:3; Num 21:14; Deut 20:13; Josh 6:2; 1 Chron 5:22; 2 Chron 14:12; 20:22; Psa 144:1; 2 Sam 22:35; Isa 42:13.
4. Israel’s conquests are the Lord’s judicial sentences on the wickedness of the Canaanite nations, Gen 15:13, 16; Deut 9:5; 12:31; 20:17.
5. Israel herself was threatened with eviction if fell into the same sins: she did, and the threat was duly carried out, Lev 26:23-33; Deut 28:15-68; 2 Chron 35:14-17; Isa 18-20; Jer 5:15-19; 6; 7:5-7; 8:10; 9:11; 25:3-9.
6. The first, and greatest, exterminations (the Flood, and Sodom) were entirely God’s, not Israel’s doing. These, like the Canaanite wars, are depicted as judgements on moral decadence (Gen 6:11-13; 18:20, etc. cf. 2 Pet 2:5f). ‘In the light of this, there is no room for the idea that Israel at war was simply mistaking her own zeal for that of God’ (Kidner). The righteous were spared, it will be noted, even in the context of an extermination decree (Noah and his family, Lot and his daughters, Rahab and her household). The Israelites at war were expected to be merciful, Deut 20:10ff; 1 King 20:31.
7. The NT wholly endorses the OT view of wars and judgements, Lk 13:1-9; Acts 7:45; 13:19; Heb 11:32-34; 12:29. It speaks of such things as signs of a world ready to perish, as summonses to repentance, and as anticipations of the final day of the Lord which will right all the injustices of history. See Lk 13:1-5. The NT is clear that the weapons of Christians are spiritual.
See Kidner, Hard Sayings: the Challenge of Old Testament Morals, 40-45.