Avery Junior Johnson was born in the sprawling industrial section of Chicago, Illinois near the Great Lakes of the United States of America. His family broke up when he was six and he was placed in the care of his Aunt by Zone Protective Services. One event that Johnson had fond memories of was his first day of church, as his Aunt tried her best to get the large shoes and small clothes of his cousins to fit him. Her religious beliefs resonated deeply within Johnson and often made him question his own decision to kill other human beings, even long after her death. However, he had no qualms about fighting the Covenant and fought actively in several campaigns to protecting humanity from their threat.

Johnson enlisted in the UNSC Marine Corps when he was nineteen and was soon thrown into the Insurrection. His name was dubiously associated with dozens of black operations and programs, including assignment to the highly classified unit called ORION Project, and participation on missions codenamed Operation: TANGLEWOOD and Operation: KALEIDOSCOPE.

Johnson was speculated to be a SPARTAN-I and may have been a member of Project: SPARTAN-I. The files that contain the records of his involvement with the program are covered up by ONI Section Zero, and anyone who tries to access them are automatically sent a fake file marked "\P_BS48789-2011-AJ.txt", also known as the "Paris/BS Spoof" File. He was a graduate of the Naval Special Warfare Sniper School (where he exceeded the expectations of his superiors), and received training in Human Entry Vehicle orbital drops, and CQB (Close Quarters Battle), while serving in NavSpecWar. He also served as a Squad Leader on many black operations missions during the Insurrection.