I really don’t see what the big deal is about this:

Documents released by the CIA show how the young agency struggled in the run-up to the Korean War and after the conflict started.

The CIA released 1,300 documents Wednesday that included 900 papers that either had not been made public earlier or contained new information. The release coincides with the 60th anniversary this month of the Korean War’s start.

One CIA analysis said “American military and civilian leaders were caught by surprise” when North Korean troops moved south across the 38th Parallel in June 1950.

“Only the intercession of poorly trained and equipped US garrison troops from Japan managed to halt the North Korean advance at a high price in American dead and wounded,” the report said.

That document, “Two Strategic Intelligence Mistakes in Korea, 1950,” also describes how U.S. military and civilian leaders were caught off-guard four months later when the Chinese “intervened in massive numbers as American and UN forces pushed the North Koreans back.”  [Stars & Stripes]

You can read the rest at the link, but it is common knowledge that both the CIA and the US military were both caught completely off guard by the North Korean and then the follow on Chinese invasions of South Korea.