Little is known of Strikers early life, other than he was brought to an Orphanage on Mars, which was secretly run by the NIA.
Harry quickly rose above his peers in the basic training, proving his leadership capabilities early on. On day one, Harry reached out to the Russel siblings and began what would become an inseparable bond.
Upon becoming leader of Lucifer Squad, Harry developed a friendly rivalry with Charlotte Winters, the leader of Reaper Squad. This rivalry continues to this day.
Unknown to any Pilot, Harry Striker was not given his role due to his Tactical Efficiency, which ranks significantly lower than his closest teammates. Instead Harry was given his role due to his unique ability to muster conviction and instill a sense of unity in his teammates.