Excerpts from Books and Wikipedia
""Between 1060 and 1076, Henry IV refuses to obey the pope, gets himself excommunicated, and is forced to stand barefoot in the snow pleading for mercy [at Canossa]. . . . Forced to forgive Henry IV as much by public pressure as by his own inclinations, Gregory VII agreed to restore the king's good standing. In return, Henry promised to recognize the pope's authority and to give up the practice of appointing his own bishops. A great reconciliation banquet followed. Henry sat at the table, silent and withdrawn, refusing to eat and drumming on the table with his fingers." [Bauer; Medieval World, p. 646] "However, Henry would have the last word. In 1084, he invaded Italy, laid siege to Rome, and deposed Pope Gregory VII. . . . Also, for Germans, Canossa is symbolic of their nation's resistance to outside interference from the Roman Catholic Church." [Furtado: 1001 Days]