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Director of National Intelligence James Clapper completed a secret mission: arrange for the release of Kenneth Bae and Matthew Todd Miller from North Korea.

The only weapon Clapper had for his cloak-and-dagger mission was a letter of introduction from President Barack Obama, according to ABC News.

Despite the highly secret nature of the trip, the Obama administration briefed some members of Congress in advance and also notified the governments of Japan, South Korea and China.

Clapper met with North Korean security officials, but not with leader Kim Jong-un.

"The officials said the short letter did not contain an apology 'in any way, shape or form,'" according to ABC News, nor was it to be a discussion about North Korea's nuclear program.

Clapper was "prepared to listen" to whatever they said about the program, but "he was not there to negotiate."