A lot has been made of the fact that with Benedict’s resignation the Roman Catholic Church will have two popes for the first time in 600 years (technically speaking, of course, Benedict is no longer pope; but you get my point). To be more precise, it was during the time span of 1378-1417. I’ll briefly explain.
The power of the papacy had surged under Innocent III (1161-1216), but suffered serious decline once Boniface VIII (1294-1303) came into office.
Following a conflict between the Pope and King Philip of France over taxation of the clergy and other issues, Boniface was deposed. Clement V became pope after Boniface died and immediately came under Philip's control. Indeed, Philip moved the papal seat from Rome to Avignon in France in 1309, inaugurating what has come to be known as The Babylonian Captivity of the Church (1309-77). During this time the papacy was the virtual pawn of the French monarchs and lost all semblance of the power it had achieved under Innocent. Still, the popes of Avignon lived in unmistakable extravagance. The Italian humanist Petrarch referred to Avignon as "the sink of every vice, the haunt of all iniquities."
It wasn't until Pope Gregory XI, with the help of St. Catherine of Siena, that the papal seat was returned to Rome, thereby ending the Babylonian Captivity. The problems for the Roman papacy, however, were far from over.
After Gregory's death, Urban VI was elected pope, but soon incurred the displeasure of the College of Cardinals in France (the story is that he was insane). The latter body elected another pope, Clement VII, who hastily retreated to . . . where else, but Avignon! Now there were two popes, one in Rome and one in Avignon (Urban was known to have tortured and murdered several cardinals in Rome who opposed him)!
This is known as The Great Schism. There is to this day disagreement among RC scholars over who was in fact the official successor to Peter during this period. After mutual denunciations and excommunications, the council of Pisa in 1409 deposed both popes and elected Alexander V. But neither of the deposed popes would leave office . . . so then there were three!! Finally, the Council of Constance in 1417 elected another pope (!), Martin V. The other three, weary of the conflict, resigned and gave Martin their support. Once again the church in western Europe had a unified leadership and the Great Schism was ended.