Stephen Colbert was a guest on the "Late Show with David Letterman" tonight and he discussed a range of topics, including his childhood and growing up as the youngest of 11 children, preparing for his own show's upcoming visit to the Middle East, and his befuddlement at why Virgin boss Richard Branson wants to fight him. Watch a clip from the interview below in which Colbert discusses going to "basic training" for his show's trip to the Middle East.