Original: The question who should invest (or more to the point, appoint) whom was the subject of an epic conflict between the Catholic church (mainly papacy) and state (mainly the Holy Roman Empire) in the Middle Ages during the so-called Investiture Controversy.
Simplified: Investiture Controversy The question who should invest (appoint) whom was the subject of a conflict between the Catholic church (mainly the papacy) and state (mainly the Holy Roman Empire) in the Middle Ages during the so-called lay investiture controversy.