assistant,
helper,
help,
supporter a person who contributes to the fulfillment of a need or furtherance of an effort or purpose; "my invaluable assistant"; "they hired additional help to finish the work"
aide -
an officer who acts as military assistant to a more senior officer
military officer,
officer any person in the armed services who holds a position of authority or command; "an officer is responsible for the lives of his men"