Saint Augustine wrote in the classic City of God, over four hundred years after Christ’s death

They who have waged war in obedience to the divine command, or in conformity with His laws, have represented in their persons the public justice or the wisdom of government, and in this capacity have put to death wicked men; such persons have by no means violated the commandment, “Thou shalt not kill.”

Saint Augustine, coincidentally during the time when Christians were being persecuted, articulated a way that God called his followers to be proactive toward evil. He believed that war was not inherently evil but, if done in the name of righteousness and for the proper reasons, was something God required us to do. | p. 153-154