American Military History, Volume 2 by Richard W. Stewart

The Western bloc was surprised by North Korea's decision to in- vade South Korea. American intelligence reports had documented the DPRK's military buildup, and by June 1950 the CIA had concluded that the DPRK could invade South Korea. Analysis of these reports by American civilian and military intelligence agencies was colored by the greater attention given to other areas of the world, previous false alarms of impending invasion, North Korean security measures, and the judgment that the DPRK was a firmly controlled satellite of the Soviet Union.

This interpretation held that the DPRK could not destroy the Republic of Korea (ROK) government without Soviet assistance and that the Soviets would not provide such assistance, fearing it would spark a general war with the United States. Instead, American intel- ligence judged that the DPRK would continue its efforts to destabilize the ROK, a conclusion reinforced by the National Assembly elections in May 1950 that highlighted widespread dissatisfaction with the Rhee government in South Korea.