In January 1077 Henry IV crossed the Alps in winter and stood outside the castle of Canossa, where Gregory VII was staying, for three days in penitential dress before being admitted and absolved. The scene became the standard image of secular power humbled by the church, and the German word for a humiliating climb-down still refers to it.
Read as politics it looks different. Henry's magnates had given him a deadline to have his excommunication lifted or lose the crown, and by presenting himself as a penitent he confronted the pope with a duty a priest cannot refuse. Gregory absolved him and lost his leverage; Henry returned to Germany, fought his opponents, and was excommunicated again three years later, at which point the sentence had lost its force. He installed an antipope and had himself crowned in Rome, and Gregory died in exile at Salerno.
The lasting outcome was structural rather than personal. Out of this struggle the Latin church emerged with its own law, its own courts, its own hierarchy of appeal terminating at Rome, and a claim to jurisdiction independent of any ruler. Historians of Western law have argued that this is where the distinction between spiritual and temporal authority as separate legal orders begins, and that a great deal of later European constitutional development follows from a quarrel about who hands a bishop his staff.