He argued for the moral reform of the Church and that the Christian West should be united under the overall leadership of the papacy. The latter was opposed by many secular rulers and the prolonged struggles that followed have come to be known as the Investiture contests. His most formidable opponent was the Holy Roman Emperor Henry IV. When in 1077 he submitted to the pope at Canossa papal supremacy seemed nearer. However, Henry’s submission was merely a tactical one and he later attacked Rome itself, forcing the pope to retreat to Salerno in southern Italy, where he died. He urged celibacy of the clergy and opposed simony.