He makes wars cease to the end of the earth; He breaks the bow and cuts the spear in two; He burns the chariot in the fire. Psalms 46:9 (NKJV)
Although war started in heaven, it did not start in or with God. It started in the mind of a creature (lucifer) that entertained and sought to carry out thoughts that are contrary to God's plans and purposes. So war has always been the result of thoughts and intents that oppose God. Yes it's written that God is a man of war and fights wars but that's to stop all the wars that came as a result of the fall of lucifer and the fall of man. God doesn't like war because it disrupts, and destroys His creation. So even in the wars that He has fought as recorded in Scripture it was to make wars cease. God finally put an end to all wars in His Son's death and resurrection on the Cross. He made peace through the Cross.