I think this is interesting.
(Intelligence)From Flynn's wiki:
He became the 18th director of the Defense Intelligence Agency in July 2012 until his forced retirement from the military in August 2014.[5][6][7] During his tenure he gave a lecture on leadership at the Moscow headquarters of the Russian military intelligence directorate GRU, the first American official to be admitted entry to the headquarters.[8][9][10]
https://en.wikipedia.org/wiki/Michael_Flynn