When discussions of war come up, people often point to Old Testament military action on the part of God’s people. Men like Joshua and David were godly men who led God’s people in battle. Then we turn over to the Psalms and see David and others praying for the destruction of their enemies. How is a Christian to understand such things?
I think we understand them within the promise made to Abraham. God promised Abraham that his descendants would inhabit the land of Canaan. The battles that Israel fought had to do with that promise. God gave them land and told them to drive out the inhabitants of that land. Along the way, the Israelites were attacked and were allowed to fight off their attackers. But once Israel reaches the Promised Land, the military action they carry out is within the confines of that land.
It’s good to keep this in mind when reading the imprecatory psalms, for example, those psalms that call down judgment on enemies. The enemies that David fought were usurpers within the land of promise. As leader of God’s people, it was his responsibility to drive out those people. No imperialism. No preventive strikes. No playing policeman in the area. God never called on his people to invade Egypt, nor Assyria, nor Babylonia. They weren’t even told to resist those attackers when they came to punish God’s people.
When Christians look for justification for modern military action, they had best look elsewhere. That justification doesn’t lie in the actions of men like Joshua or David.