Pope Benedict has led the Catholic Church since 2005, and his papacy has reflected his belief that the Catholic Church should retain its core traditional, conservative values in an era of rapid change.
He rejected calls for a debate on the issue of clerical celibacy, and reaffirmed the ban on Communion for divorced Catholics who remarry. He has also said the Church's strict positions on abortion, euthanasia and gay partnerships were "not negotiable".
This outspoken orthodoxy has divided liberals and more traditional Catholics, while the recent leaking of personal documents suggests a lack of control over the machinations of the Vatican.
How has Benedict XVI managed the world's largest Christian community? We asked six scholars and analysts for their perspective on key areas of the pontificate.
Governance - Clifford Longley
Pope Benedict was clearly shocked and disappointed that one of those closest to him, his butler Paolo Gabriele, had been a source of the leaked Vatican documents that revealed a state of turmoil inside the central government of the Catholic Church.
The Curia - the central government of the Church - appeared to be riddled with rival factions and there were accusations of corruption in high places.
Observers had long labelled the Vatican a dysfunctional institution - now the details were laid bare.
Many curial officials, men dedicated to the good of the Church, felt frustrated and exasperated by the institutional sclerosis they encountered.
Pope Benedict may well have realised that in his 86th year he no longer had the energy to do what needed to be done to sort this all out.
That, and his inability to go on travelling the great distances that the job demands, may well have been what persuaded him to abdicate - for the good of the Church.
The reform of the Vatican, which he had only begun at the margins, has a long way to go yet.
Decentralisation is now imperative. His successor has a huge and unenviable task.
Evangelisation - Austen Ivereigh
In speeches, addresses and teaching documents Benedict XVI considered how to present the Gospel to cultures steeped in Christian values yet often hostile to the Church.
This specific challenge, known as the "new evangelisation" ("new" referring to the context rather than the message), was one of Pope Benedict's priorities: he created a new Vatican department to promote it, and last October called together the world's bishops to agree how to take it forward.
FULL STORY Viewpoints: successes and failures of Benedict XVI (BBC)