Conversation so far:
What did John O. Brennan do as an advisor to Barack Obama?
John O. Brennan served as chief counterterrorism advisor to U.S. President Barack Obama, with the title Deputy National Security Advisor for Homeland Security and Counterterrorism, and Assistant to the President.
When did John O. Brennan begin as Deputy National Security Advisor for Homeland Security and Counterterrorism?
In late 2008.
What else did John O. Brennan do as Deputy National Security Advisor for Homeland Security and Counterterrorism?
John O. Brennan's responsibilities included overseeing plans to protect the country from terrorism and respond to natural disasters, and he met with the president daily.

Question: Did he have any notable moments under Obama?
Self-contained rewrite: Did John O. Brennan have any notable moments under Barack Obama?