One man has the unique distinction of leading the miltary arm of U.S. government through two successive presidential terms. But former Defense Secretary Robert Gates' work in government long predates his appointment by President Bush and retention by President Obama.

Dr. Gates spent 26 years in the CIA and National Security Council, and he was CIA director in the early 1990s. He has a new memoir called "Duty: Memoirs of a Secretary at War," and he'll be speaking tonight at the Kimmel Center in Philadelphia as part of the Philadelphia Speakers Series.

Before his Kimmel Center appearance, Robert Gates spoke with "NewsWorks Tonight" Producer Shai Ben-Yaacov.