The G.I. Joe team's de facto leader, Sergeant Conrad Hauser, a.k.a, Duke, is an honorable and straightforward military man. He tends to be stubborn and stoic, and puts the safety of his teammates and his family first, even if they protest.
On the show, his typical attire is a combat uniform, with a beige vest over a gray and olive short-sleeved shirt with shoulder pads, with olive drab cargo pants.
Duke was once a rising football star in high school, but an injury in his senior year ruined his chances at getting a college scholarship. Flint, who was indirectly responsible for his injury, later helped him out by suggesting he join the Army.
During his career in the military, Duke distinguished himself with exceptional skills and athletic prowess. In the field of battle, he saved the lives of his fellow soldiers several times.
One day, he was summoned to join Lt. Shana O'Hara's team and investigate a "terrorist threat" on Cobra Industries. They did not get on well at first, but after the destruction of a Cobra laboratory saw them framed as criminals, they were forced to remain together as fugitives.