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.