The war of 1950-1953 in Korea was the first war by the United Nations against an aggressive state in the twentieth century. The war was also the most significant conflict to emerge at the beginning of the Cold War and it leaded to be decisive the route of the Cold War. The Korean War was not only considerable reflection of the United States and the Soviet Union confrontation, but also they avoided direct combat each other in this conflict. This war shaped again how the West and the East dealt with each other and also caused part of a revolution in war in history. Indeed, without the Korean war, no other possible event could have created the impact of Korea on diplomatic and military options in world politics. The Korean war has created a situation where it avoided an important perceived war threat that reveals high-level conflicts and policies that it was associated with the cold war. In this context, this paper will examine the main military, diplomatic and political issues of the Korean War. The aim of this paper is to explore the characteristics and nature of Korean War, and also to examine why the Korean War was the birthplace of doctrine of limited war at beginning of the Cold War. In this way, it can be understood why the Korean war strongly influenced world politics, and how it created most of the features of the cold war.