Mercy was one of three hospital ships, the others being USS Comfort (AH-6) and USS Hope (AH-7), built, commanded and crewed by the Navy for the Army. These ships, unlike the Navy hospital ships, were intended for evacuation and transport of patients after primary care had been given. Medical equipment and personnel were provided by the Army. The Army medical complement table of organization provided for the temporary reinforcement of the staff if the ship directly supported amphibious operations.