RAY SUAREZ: The world witnessed something today it had not seen since the 15th century: A sitting pope, Benedict XVI, announced he is giving up the papacy.
The news reverberated around the globe and stunned many of the world's 1.2 billion Catholics.
JEFFREY BEDIA, Washington: It was a big surprise because this doesn't happen all the time. And my first reaction was to pray and to call my friends, texted my friends, and asked even my non-Catholic and non-believing friends to keep us in their thoughts and their prayers.
CRISTINA AGUIRRE: I had never heard anything like this in my life. The pope has to be there until he dies. And he is resigning?
LUCERA MORI, Rome: The pope can't resign. This hasn't happened since Celestine V. A pope can't resign. This news isn't right.
RAY SUAREZ: In fact, Pope Celestine V abdicated in 1294, but the last pontiff to do so was Gregory XII in 1415. Pope Benedict's decision at age 85 came in an announcement made in Latin during a meeting of cardinals at the Vatican.
POPE BENEDICT XVI: Dear brothers, I have convoked you to this consistory not only for the three canonizations, but also to communicate to you a decision of great importance for the life of the church.
After having repeatedly examined my conscience before God, I have come to the certainty that my strengths due to an advanced age are no longer suited to an adequate exercise of the papal ministry.
RAY SUAREZ: Underscoring that point, Benedict's brother, Georg Ratzinger, said today the pope's doctors recently advised him not to take any more transatlantic trips. In a 2010 interview, Benedict said a pope could step down if he felt unable physically to carry on. And he had visibly slowed in the last few years.
ARCHBISHOP LOUIS SAKO, Head of Chaldean Catholic Church: I was the last one who met the pope last week, and I felt that he was tired and he said just a few words.
RAY SUAREZ: Still, few outside his innermost circle saw it coming. And the announcement instantly sparked speculation about whether there was something more to the decision.
RONALD DUNN, Munich: It's unique in terms of the papacy. So it could be deeper than what we have been told at the moment.
ANDREA WORMSDORF, Munich: I can only accept his resignation if he were ill and could therefore no longer carry out his post, but I can't accept any other reason, none whatsoever.
RAY SUAREZ: A Vatican spokesman insisted the pope had no specific medical problem and that he came to this decision on his own without any outside pressure.
FR. FEDERICO LOMBARDI, Vatican Spokesman: He says this with great freedom and clarity. And we admire his totally freedom in renouncing to his service.
RAY SUAREZ: Benedict's actions stood in particular contrast to that of Pope John Paul II, his immediate predecessor, who served 27 years, the second longest of any pope. During that tenure, John Paul was shot by a would-be assassin and later contracted Parkinson's disease.
In his last years, he struggled to walk, speak, and even listen until his death in 2005. Days later, white smoke arose from the chimney of the Sistine Chapel to signal Cardinal Joseph Ratzinger's election. He was at 78 the oldest pope elected in nearly 300 years. The future Benedict XVI was born in Germany in 1927, an archbishop of Munich and then cardinal.
For nearly three decades, he was one of Pope John Paul's most trusted aides, enforcing conservative doctrine. As pope, he warned against growing secularism in the West. It wasn't always a popular stance in Europe and North America, as evidenced today.
SHERRI HARNICK, New York: In the next pope, we need somebody who will modernize the church somewhat and move with the times, so that they don't lose their audience and all the younger people.
MAN: Hopefully, the next pope will be eventually a little bit better and more inclusive than this one was.
RAY SUAREZ: But Benedict was undeterred by such views. He suggested as much in his 1996 book, "Salt of the Earth," in which he wrote: "Maybe we're facing a new and different kind of epoch in the church's history, where Christianity will again be characterized more by the mustard seed, where it will exist in small seemingly insignificant groups that nonetheless live in intensive struggle against evil."
To that end, the pontiff focused on promoting Roman Catholic growth in Latin America and Africa. He also made use of Twitter and other social media to reach new and younger audiences worldwide. And he sought to reach out across faiths, but with decidedly mixed results.
In 2011, he formally announced the Jewish people shouldn't be condemned for the death of Jesus, but he angered many Jews by lifting the excommunication of a conservative British bishop who denied the Holocaust. In 2006, Benedict quoted a Byzantine emperor speaking on the Prophet Mohammed.
POPE BENEDICT XVI: Show me just what Mohammed brought that was new and there you will find things only evil and inhuman, such as his command to spread by the sword the faith he preached.
RAY SUAREZ: Outraged Muslims burned the pope in effigy. He later visited the Blue Mosque in Istanbul, Turkey, to pray with the grand mufti in a bid to restore calm. A fire he could not extinguish was the ongoing scandal involving sexual abuse of children by priests in country after country.
Two years ago, letters emerged showing that as cardinal in charge of handling the growing crisis, Benedict resisted removing priests accused of being child molesters. And last fall, the pope's former butler was convicted of leaking personal documents. Some pointed to alleged mismanagement at Vatican lending institutions.
Now the Roman Catholic world awaits a successor to chart the direction of the church and address lingering scandals. Pope Benedict officially steps down Feb. 28. Then the College of Cardinals will meet in a papal conclave held in the Sistine Chapel to elect a new pope.
By Vatican law, all cardinals under 80 at the time of voting are allowed to cast a ballot; 118 now meet that standard.
CARDINAL CHRISTOPH SCHOENBORN, Archbishop of Vienna: Without doubt, this is an historic moment. Right now, 1.2 billion Catholics the world over are holding their breath.
RAY SUAREZ: Benedict himself will have no official role in choosing his own successor, but 67, more than half the voting-eligible cardinals, were appointed by him, including the archbishop of Washington, Cardinal Donald Wuerl.
CARDINAL DONALD WUERL, Archbishop of Washington: We will be looking for someone who is a very articulate voice in that continuity. But I think we also will be looking for someone who will carry on the spiritual tradition that Pope Benedict has so focused on.
RAY SUAREZ: More than half the current cardinals come from Europe, but more than half the world's Catholics now live in Africa and Latin America. And already there's speculation the next pontiff may be the first non-European ever.