Keeping Pyongyang under constant military pressure has been part of a long-standing goal of the U.S. - in tandem with its South Korean ally - to bring North Korea to the brink of collapse by pushing Pyongyang into accrued defense spending to the detriment of its economic development.After the conflict between rival capitalist powers was settled in 1945, the US assumed the leadership in the defense, and promotion, of capitalism by absorbing the British Empire into an empire under its control (read The Anglo-American Establishment by Carroll Quigley). At the same time the new US hegemony went immediately after its primary adversary, the Soviet Union. There was a seamless transition from the defeat of their capitalist rivals--Germany, Italy, and Japan--to the war against the USSR whose resources, labor, and markets were not accessible by Western capitalists due to the nature of their command economy under the control of a centralized bureaucracy.
In southern Korea, soon to become South Korea under US control, this new war against USSR informed US policies for this country by supporting the previous repressive police and government structures that had characterized capitalist and landlord class rule when they were under Japanese control. The US made considerable use of all Koreans who had faithfully served under the Japanese imposed regime and even used some former Japanese officials. Both groups were extremely hated by all Korean patriots and soon there were uprisings all over southern Korea against the US imposed government. From 1946 till the outbreak of the war the South Korean government under the US puppet, Syngman Rhee, used the most brutal methods of suppression imaginable against these populist movements.
As 1950 approached, they had largely succeeded in wiping out the opposition, and as a result, the US and its South Korea regime turned their attention northward. (To read all the details of this tragedy, read the extensively documented book by Bruce Cumings entitled, The Origins to the Korean War, v.1. Unfortunately, the book is not easily obtainable, and I suspect for political reasons.)
Thus, one can see that the Korean War never ended either formally or in reality. It is still being fought because the US Empire cannot tolerate opposition to, or independence from, its influence and its economic system.