Chaplain joined the Tank Police unit after a critical incident during his service as a regular officer. He had shown leniency to a criminal who then shot and killed his partner before escaping, prompting his reassignment.

Within the Tank Police, he serves dual roles as both an unofficial police chaplain and an active tank pilot. His background as a chaplain is evident in his frequent references to biblical teachings, which he uses for guidance and inspiration during operations. He shares a professional relationship with fellow officer Jim E. Lovelock, known as Specs, characterized by a friendly rivalry during their duties.

Physically, Chaplain has black hair and a mustache. He operates tanks alongside other unit members, combatting crime in Newport City. In later continuations like the New Dominion Tank Police OVA series, his role persists with the unit, though he is occasionally referred to by the alternate designation "Reverend" or "Rev." His involvement remains consistent as a supporting member of the Tank Police team across all appearances, including spin-offs like Dominion Conflict One: No More Noise, with no substantial new backstory or character development provided beyond his established history and duties.