Duke is the code name of First Sergeant Conrad S. Hauser. He is field commander and second-in-command of the G.I. Joe Team after Hawk. He is one of the key characters of G.I. Joe and a fan-favorite. He is generally regarded by fans as a main character, despite not appearing in the comic series for a number of issues, nor was he one of the original toys.
His file states that he hails from St. Louis, Missouri and is fluent in English, French and German, as well as several Southeast Asian dialects. He was at the top of his class at Fort Benning, has undergone Special Forces training and worked with South Vietnamese Tribesmen. He was also an instructor in four different Special Forces schools. Despite his accomplishments, he has repeatedly turned down any officer commissions offered to him. He believes a commander's place is with his troops, not behind the battle lines. [wiki]