Conversation so far:
What were John O. Brennan's career highlights?
President Barack Obama nominated John O. Brennan to be director of the Central Intelligence Agency. He was sworn into the office of CIA Director on March 8, 2013.
What is notable about John O. Brennan's time at the CIA?
Two months after assuming his post at the CIA, John O. Brennan replaced Gina Haspel, head of the National Clandestine Service with another unidentified, career intelligence officer and former Marine.

Question: What did he do under President Bush?
Self-contained rewrite: What did John O. Brennan do under President George Bush Jr.?