NSC-68 was one of a number of U.S. Government responses to the intelligence that the Soviet Union had "probably" achieved a successful nuclear explosion in August 1949.
State and Defense, Secretaries of
"NSC-68: A Report to the National Security Council,"
Naval War College Review: Vol. 28
, Article 7.
Available at: http://digital-commons.usnwc.edu/nwc-review/vol28/iss3/7