From ancient times, many war historians have strongly recommended posterity to make their future better through the understanding of wars. This lesson is valid in the modern age as well. In other words, it means that the ability to prevent wars and even if already occurred, the ability to minimize the damages caused by them derive from understanding accurately them. Thus, in this study, the author attempted to find out how to create the more peaceful world in the manner of analyzing the concept of preemption that has drawn attention recently.
To do so, as a result of analyzing a tendency among the previous relevant studies, it was found that the fields where there were lack of studies on preemption until now concerned the pure conception. Accordingly, the author tried to investigate the historical cases and the factors to affect transitions in the recognition of war justification on the basis of such the concept.
While ethically, preemption can be justified in the conceptional aspect, in actuality it seems to be degenerated into an aggressive concept addressed at the level of national security strategies among the powers of the world. Therefore, the criteria on ‘imminent threat' should be established so that preemption ensures the nation's right of self-defense and further remains as the concept of using the sword for the sake of justice. If accomplished, the bloody history of mankind will be made more wishful in future.