An argument went on between Gregory and Henry. This argument was on whether Henry or Gregory should choose the next Bishop. Gregory got rejected by the Roman's on whether he should pick the next Bishop because of Henry. So Gregory "Excommunicated" Henry. Henry then traveled to Italy to apologize to Gregory. Before Gregory forgave him Henry stood out in the snow for three days out side of Gregory's room.
Pope Gregory died leaving Henry iv to do as he pleased
Henry crossed the freezing Alps to the Italian town of Canossa. He approached the castle where the Pope Gregory VII was a guest and then begged humbly to be forgiven.
It's because Henry's nobles supported Gregory, and the reason why Henry begged the Pope was because he said the Pope had no real authority.
Henry IV of Germany told him to resign. In exchange, Gregory excommunicated Henry and remained as pope.
Pope Gregory VII.
Henry lV violated the pope's orders.
pope Gregory VII wanted to change the rules about the religion. Henry IV got angry and thought he can fire pope Gregory VII. Henry got excommunicated from the church. years past, he came back and begged for forgiveness and was back in the church society.
Investiture Controversy - Henry felt that he, as emperor, had the right to appoint any bishops in his kingdom. Gregory insisted that only the pope could appoint them.
Henry lV violated the pope's orders.
Pope Gregory excommunicated King Henry IV while Henry declared the pope deposed. Most of the people seemed to support the actions of the pope and not those of Henry.
Pope Gregory VII
Pope Gregory VII