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John Owen Brennan (born September 22, 1955) was the Director of the Central Intelligence Agency (CIA) from March 2013 to January 2017. He served as chief counterterrorism advisor to U.S. President Barack Obama; his title was Deputy National Security Advisor for Homeland Security and Counterterrorism, and Assistant to the President. His responsibilities included overseeing plans to protect the country from terrorism and respond to natural disasters, and he met with the President daily. Previously, he advised President Obama on foreign policy and intelligence issues during the 2008 presidential campaign and transition.

Brennan began his CIA career as an analyst and spent 25 years with the agency. He was a daily intelligence briefer for President Bill Clinton. In 1996, he was CIA station chief in Riyadh, Saudi Arabia when the Khobar Towers bombing killed 19 U.S. servicemen. In 1999, he was appointed chief of staff to George Tenet, then-Director of the CIA. Brennan became deputy executive director of the CIA in March 2001. He was director of the newly created Terrorist Threat Integration Center from 2003 to 2004, an office that sifted through and compiled information for President Bush's daily top secret intelligence briefings and employed the services of analysts from a dozen U.S. agencies and entities. One of the controversies in his career involves the distribution of intelligence to the Bush White House that helped lead to an "Orange Terror Alert", in late 2003. The intelligence, which purported to list terror targets, was highly controversial within the CIA and was later discredited. An Obama administration official does not dispute that Brennan distributed the intelligence during the Bush era but said Brennan passed it along because that was his job. His last post within the Intelligence Community was as director of the National Counterterrorism Center in 2004 and 2005, which incorporated information on terrorist activities across U.S. agencies.  Brennan then left government service for a few years, becoming Chairman of the Intelligence and National Security Alliance (INSA) and the CEO of The Analysis Corporation (TAC). He continued to lead TAC after its acquisition by Global Strategies Group in 2007 and its growth as the Global Intelligence Solutions division of Global's North American technology business GTEC, before returning to government service with the Obama administration as Homeland Security Advisor on January 20, 2009.  On January 7, 2013, Brennan was nominated by President Barack Obama to be director of the Central Intelligence Agency.  In September 2017, Brennan was named a Distinguished Non-Resident Scholar at The University of Texas at Austin, where he also acts as a Senior Advisor to the University's Intelligence Studies Project.

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Brennan then left government service for a few years, becoming Chairman of the Intelligence and National Security Alliance (INSA)