The Korean Armistice Agreement of 1953 brought the hostilities to a close with a cease fire. The U.S. broke the agreement in 1956:
“Paragraph 13(d) of the Armistice Agreement mandated that neither side introduce new weapons into Korea, other than piece-for-piece replacement of equipment. In September 1956 the U.S. Chairman of the Joint Chiefs of Staff Admiral Radford indicated that the U.S. military intention was to introduce atomic weapons into Korea, which was agreed to by the U.S. National Security Council and President Eisenhower. However paragraph 13(d) prevented the introduction of nuclear weapons and missiles. The U.S. unilaterally abrogated paragraph 13(d), breaking the Armistice Agreement, despite concerns by United Nations allies. At a meeting of the Military Armistice Commission on June 21, 1957, the U.S. informed the North Korean representatives that the United Nations Command no longer considered itself bound by paragraph 13(d) of the armistice. In January 1958 nuclear armed Honest John missiles and 280mm atomic cannons were deployed to South Korea, a year later adding nuclear armed Matador cruise missiles with the range to reach China and the Soviet Union.”
UPDATE: August 10, 2017
US Foreign Policy puts its own people at risk. Foreign policy is not a policy of a national security. That concept is a joke. Read Rozeff’s follow-up:
The 1953 Armistice in Korea was followed two months later by the “Mutual Defense Treaty Between the United States and the Republic of Korea“. This commitment on the part of the U.S. was a mistake. It was an entangling alliance with far-reaching consequences. This brought S. Korea under the nuclear bomb protection umbrella of the U.S., and this gave N. Korea an incentive to develop nuclear weapons. It lent permanence to the U.S. as an enemy of N. Korea. It gave the S. Koreans a negative incentive to negotiate a permanent peace with N. Korea.
The two Koreas on 19 February 1992 committed themselves to a treaty ban on nuclear weapons. However, they could not agree on inspections. Joint military exercises of S. Korea and the U.S. were a sticking point, again being negative fallout from the U.S. defense treaty with S. Korea.
When and if, or even before, N. Korea has the capability to launch a nuclear-tipped missile aimed at Washington or Los Angeles or a city in between, there arises a strategic problem that stems from that 1953 defense treaty but was entirely unforeseen at that time: Why should Washington be willing to defend S. Korea and open itself to such a nuclear threat? Why should Washington be willing to exchange Washington for Seoul?
Since Washington is not willing to face such an exchange, there exists now a hair-trigger situation. The more that N. Korea’s nuclear and missile capabilities mature and the more that its leader threatens the U.S., the closer the U.S. gets to a pre-emptive attack on N. Korea. Furthermore, the U.S. is getting closer to an attack triggered by some military movements or preparations in N. Korea that can be construed as precursors to an attack of some sort.