Each of these positions has a history and each of these positions has claimed biblical authority and support. War, just like any other biblical topic, has been subject to various interpretations. Before we can think theologically about the conduct of war and in war, we must think theologically about the cause of war. In short, we must consider war and the problem of evil. Our sin nature corrupts international relations as well as interpersonal relations.
War is ultimately a reflection of and consequence of sin.
Wars are fought on the battlefields of the globe, but they are waged first in human heart. The Christian conscience has throughout history recognized the tragic character of war. The issue that tears the Christian conscience is not whether war is good, but whether it is in all cases avoidable. For a Christian to think about and wrestle with the issues of war is to struggle with the problem of evil. How those passages are interpreted determines the position that one holds.