Billison, who landed at Iwo Jima with the U.S. Marines and went on to receive a Congressional Silver Medal, was recruited to help translate radio communications into Navajo-language code.
In 2000, he was approached by the Hasbro toy company to be the voice of its new Navajo Code Talker GI Joe doll. He recorded seven Navajo phrases for the doll at his home on the reservation in Kinlichee, Ariz.
After the war, he earned a doctorate in education and sat on the Kinlichee school board.
"Dr. Billison led an extraordinary life," Lawrence Morgan, speaker of the Navajo Nation Council, said Wednesday. "Dr. Billison never stopped advocating for both veterans and youth."
Billison, who was born on the floor of a hogan in the mid-1920s, did not have a birth certificate, but is believed to have been about 78 years old when he died.