From the 11th to the 14th centuries there was a constant struggle between the papacy and the emperor for supremacy. The struggle began over investiture but by the 13th century had expanded to fundamental questions over theology and the right to rule. After decades of open warfare in Northern Italy, Charles IV and Pope Clement VI finally resolved the dispute in the Concordat of Prague in 1367, whereby the papacy fell under full control of the emperor. By the mid-15th century, the emperor crowned the pope, not the other way around. Within 50 years of that, the reformist emperor Charles VI selected a relatively unknown monk from Germany as the pope, Martin Luther aka Pope Innocent V, who launched massive reforms of the Catholic Church, most famously the acceptance of marriage among the clergy and the end to the indulgences What if the papacy had managed to win the investiture controversy before the struggle expanded beyond it into more fundamental questions? How different would the Catholic Church look today?