Problem: In 1 Chronicles 5:18–22, the war of the sons of Reuben, the Gadites and the half tribe of Manasseh, against the Hagrites is described. Verse 20 states that the children of Israel cried out to the Lord in the midst of the battle, and God helped them in their fight against the Hagrites. In fact, verse 22 states, “for many fell dead, because the war was God’s.” However, if God is good (Ps. 100:5) and if God is the God of peace (Rom. 15:33), how can He make war?
Solution: Waging war and being a God of goodness and peace are not necessarily incompatible. First, it is wrong to suppose that waging war is inconsistent with goodness. A surgeon takes drastic action against a cancer to bring about the ultimate good of the patient. Yet, spiritual evil is much more serious than physical evil. When God waged war in the OT, it was against the forces of spiritual evil. God took drastic action to rid the land of the evil influence of the inhabitants.
Second, it is wrong to suppose that waging war is inconsistent with peace. There would be no peace in the world if God did not oppose evil. Indeed, the peace of God is now available to all who believe, because God waged war against the forces of evil—a warfare that culminated at the Cross where the blood of God’s only Son was shed. Ultimately, the enemy will be cast into the lake of fire as a defeated foe. Sometimes war is necessary to bring about lasting peace.
Because God is good, He never wages war in an unrighteous manner. Because God is the God of peace, He only wages war against the enemies of peace. God is the God of war because He has defeated the forces of evil who would bring upon all people spiritual destruction forever.