(Pope Benedict XVI waves as he arrives to lead the Wednesday general audience in Saint Peter’s square, at the Vatican October 24, 2012. REUTERS/Giampiero Sposito)

In Havana last March, when Pope Benedict sat down with Fidel Castro, the revolutionary leader jocularly asked his fellow octogenarian: “What does a pope do?”

Benedict proceeded to tell Castro, who had stepped down as president in 2008 for health reasons and had to be helped to walk into the room, about his duties as leader of the 1.2 billion-member Roman Catholic Church.

Little did Castro know that Benedict was himself contemplating retirement.

A pope has not abdicated in some six centuries, and the Catholic faithful have come to expect the man whose titles include successor of St. Peter and “servant of the servants of God,” to stay in office until his dying breath. His decision to take that step, just under a year later, would shake the foundations of a Church already reeling from a series of scandals – from problems at the Vatican Bank to allegations of sexual abuse – and facing challenges to its authority around the world.

Back home in the Vatican in the weeks after his Cuba visit, Benedict spent time in the prayerful silence of his small private chapel in the Vatican’s Apostolic Palace where a large bronze Christ on a crucifix looks down from a wall. At some point last spring he decided he should go.