A look at the career of John Brennan, Assistant to the President for Homeland Security and Counterterrorism.
From left to right, Frances Fragos Townsend, former Assistant to the President for Counterterrorism and Homeland Security, John Brennan, Assistant to the President for Homeland Security and Counterterrorism, and George Tenet, former Dir. of the CIA, are seen on the tarmac before boarding their plane at Andrews Air Force Base, June 19, 2012.
President Barack Obama reacts as Counterterrorism chief and adviser John Brennan briefs him at the White House on the details of the shootings at Sandy Hook Elementary School in Newtown, Connecticut, December 14, 2012.
President Barack Obama speaks at the Federal Emergency Management Agency (FEMA) Headquarters in Washington, Oct. 31, 2012. Third from left are, Assistant to the President for Homeland Security and Counterterrorism John Brennan, FEMA administrator Craig Fugate, the president and Homeland Security Secretary Janet Napolitano.
Vice President Joe Biden (center) talks with John Brennan (left) President Obama's chief counterterrorism adviser and former Director of the CIA David Petraeus (right) following a swearing-in ceremony in the Roosevelt Room of the White House in Washington, Sept., 6, 2011.
John Brennan, President Barack Obama's counterterrorism adviser, left, and Principal Deputy Press Secretary Josh Earnest, walk to board the Marine One helicopter as they prepare to depart with President Barack Obama from the South Lawn, Aug. 18, 2011.
Deputy National Security Adviser for Homeland Security and Counterterrorism John Brennan (left) and White House Press Secretary Jay Carney participate in the daily news briefing at the White House, May 2, 2011.
Deputy National Security Adviser for Homeland Security and Counterterrorism John Brennanl (left) and former White House Press Secretary Robert Gibbs brief reporters at the White House in Washington, Oct. 29, 2010.
H1N1 swine flu virus talks in the Rose Garden, Sept. 1, 2009.
John Brennan, President Barack Obama's top adviser for counterterrorism and homeland security, (left), meets with Yemen's President Ali Abdullah Saleh at the presidential palace in San'a, Yemen, March 16, 2009.
John Brennan (left), assistant for counterterrorism and homeland security, Carlos Pascual (center), U.S. ambassador to Mexico, and General Victor Renuart, commander of the Northern Command, stand next to a Bell helicopter 412 as they listen to the U.S anthem during a ceremony in Mexico City December 15, 2009.