Indeed, throughout the Old and New Testament, God ordained war as an instrument of justice. They are described as servants of God empowered with the sword. War in defense of the innocent is not murder. God does require restraint in deciding to wage war or in waging war. A just war must be waged by a legitimate government, for a legitimate cause, with a legitimate purpose, with consideration of benefits and costs, with means proportionate to the offence, and recognising the difference between civilians and soldiers.
War is an abnormal business, also in the Bible.
The goal of war must always be peace, and any programme or armament must be pursued in the context of preserving peace.