Pope Benedict XVI (file photo)

Pope Gregory XII was the last pontiff to resign the papacy.  But that's only one part of a story of church and political intrigue from the 1400s.  His resignation was not entirely voluntary.

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"Technically, he did abdicate," says Tom Davis, Professor of Religious Studies, IUPUI.  "But it was under duresss.  It wasn't the sort of resignation that we seem to have going on with Benedict XVI."

Gregory was pope during a period of turmoil known as the Western Schism when the church was divided between rival popes, both having their own loyal cardinals and followers.  The conflict last four decades, ending finally in 1417 when the Council of Constance chose a new pope who took the name Martin V.  

"From the church's point of view, it's more proper to talk about a pope and the anti-popes rather than there being two or three popes," says Davis.  "But you know what?  For the people of the time period, all they knew was...there being some confusion over who was the real pope."

Gregory XII and his rival, John XXIII of Pisa, were both made cardinals as a reward for stepping down.  

Born to a noble family in Venice about 1327, Gregory XII is recognized by the church as the true pope of his era.  He has won praise for centuries for resigning for the good of the church.