VATICAN CITY — Citing advanced years and infirmity, but showing characteristic tough-mindedness and unpredictability, Pope Benedict XVI shocked Roman Catholics on Monday by saying that he would resign Feb. 28, becoming the first pope to do so in six centuries.
Speaking in Latin to a small gathering of cardinals at the Vatican on Monday morning, Benedict said that after examining his 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 leading the world’s 1 billion Roman Catholics.
The statement, soon translated into seven languages, ricocheted around the globe.
A shy, tough-minded theologian who seemed to relish writing books more than greeting stadium crowds, Benedict, 85, was elected by fellow cardinals in 2005 after the death of John Paul II. An often divisive figure, he spent much of his papacy in the shadow of his beloved predecessor.
Above all, Benedict’s papacy was overshadowed by clerical abuse scandals, a case involving documents leaked from within the Vatican, and tangles with Jews, Muslims and Anglicans. In his handling of the sexual abuse crisis, critics said that his failures of governance were tantamount to moral failings.
In recent months, Benedict had been showing signs of age. He often seemed tired and even appeared to doze off during Midnight Mass on Christmas Eve, after being taken to the altar of St. Peter’s on a wheeled platform. But few expected the pope to resign so suddenly, even though he had said in the past that he would consider the option.
‘'The pope took us by surprise,’’ said the Vatican spokesman, the Rev. Federico Lombardi, expounding on one of the most dramatic moments in centuries of Vatican history.
He appeared at a hastily called news conference Monday, where he stood by himself at the lectern, with an unopened bottle of mineral water and a dog-eared copy of a Canon Law guide before him.
Lombardi said the pope would continue to carry out his duties until Feb. 28 at 8 p.m., and that a successor would probably be elected by Easter, which falls on March 31. But he said the timing for an election of a new pope is ‘‘not an announcement, it’s a hypothesis.’’
He said the pope did not display strong emotions as he made his announcement but spoke with ‘‘great dignity, great concentration and great understanding of the significance of the moment.’’
The announcement plunged the Roman Catholic world into intense speculation about Benedict’s successor and seemed likely to inspire many contrasting evaluations of a papacy that was seen as both traditionalist and contentious — though perhaps not so confrontational as many had feared of the man they called ‘‘God’s Rottweiler’’ for his tenacious defense of church doctrine.
Benedict was deeply distraught about the decline in religious belief in the West, and he had spent the previous 25 years as the head of the Vatican’s doctrinal office, the Congregation for the Doctrine of the Faith. There, he had watched his beloved predecessor, John Paul II, slowly decline with Parkinson’s disease.
''In today’s world,’’ Benedict said in his announcement, ‘‘subject to so many rapid changes and shaken by questions of deep relevance for the life of faith, in order to govern the bark of St. Peter and proclaim the gospel, both strength of mind and body are necessary, strength which in the last few months has deteriorated in me to the extent that I have had to recognize my incapacity to adequately fulfill the ministry entrusted to me.’’
''For this reason,’’ he continued, ‘‘and well aware of the seriousness of this act, with full freedom, I declare that I renounce the ministry of bishop of Rome, successor of St. Peter.’’
At the news conference, Lombardi noted that in a 2010 book-length interview with a German journalist, Benedict had said that, ‘‘if a pope clearly realizes that he is no longer physically, psychologically, and spiritually capable of handling the duties of his office, then he has a right and, under some circumstances, also an obligation to resign.’’
Benedict’s brother, the Rev. Georg Ratzinger, said that the pope’s weakening health had led him to step down.
‘'His age was taking its toll,’’ the 89-year-old told the German news agency Deutsche-Presse Agentur on Monday, adding that he had been aware of his brother’s plan for several months.
Lombardi said the pope would retire first to his summer residence in Castel Gandolfo, in the hills outside Rome, and later at a monastery in Vatican City.
Benedict, the former Cardinal Joseph Ratzinger, was elected April 19, 2005. At the time of his election, Benedict was a popular choice within the college of 115 cardinals who chose him as a man who shared — and at times went beyond — the conservative theology of his predecessor and mentor, John Paul, and seemed ready to take over the job after serving beside him for more than two decades.
The church’s 265th pope, Benedict was the first German to hold the title in half a millennium, and his election was a milestone toward Germany’s spiritual renewal 60 years after World War II and the Holocaust. At 78, he was also the oldest new pope since 1730.
But Benedict was seen as a weak manager, and his papacy was troubled by debilitating scandals, most recently ‘‘Vatileaks,’’ in which his butler was convicted by a Vatican court in October of aggravated theft after he admitted stealing confidential documents, many of which wound up in a tell-all book that showed behind-the-scenes Vatican intrigue.
Above all, Benedict’s tenure was entangled in growing sexual abuse scandals in the Roman Catholic Church that crept ever closer to the Vatican itself.
In 2010, as outrage built over clerical abuses, some secular and liberal Catholic voices called for his resignation, their demands fueled by reports that laid part of the blame at his doorstep, citing his response both as a bishop long ago in Germany and as a cardinal heading the Congregation for the Doctrine of the Faith, which handles such cases.
In one disclosure, news emerged that in 1985, when Benedict was Cardinal Ratzinger, he signed a letter putting off efforts to defrock a convicted child-molesting priest. He cited the priest’s relative youth but also the good of the church.
For his supporters, it was a painful paradox that the long-gathering abuse scandal finally hit the Vatican with a vengeance under Benedict. As the church’s doctrinal leader he had been ahead of many of his peers in recognizing how deeply the institution had been damaged. As early as 2005, he obliquely referred to priestly abuse as a ‘‘filth in the church.’’
He went on to apologize for the abuse and met with victims, a first for the papacy. But he could not escape the reality that the church had shielded priests accused of molesting, minimized behavior it would have otherwise deemed immoral and kept it secret from the civil authorities, forestalling criminal prosecution.
‘'Having wielded power so aggressively in an intellectual sphere, he became pope and shrank from the full power of the office, refusing to prosecute guilty cardinals and bishops who recycled predators in the abuse crisis,’’ said Jason Berry, the author of ‘‘Render Unto Rome,’’ about the Vatican’s finances, and other books on the abuse crisis.
‘'He approved an investigation of nuns for straying from doctrine, yet failed to confront the antiquated tribunal system that gives men in the highest offices of the church de facto immunity from justice,’’ Berry added.
Born April 16, 1927, in Marktl am Inn, in Bavaria, he grew up the son of a police officer. He was ordained in 1951, at age 24, and began his career as a liberal academic and theological adviser at the Second Vatican Council, supporting many efforts to make the church more open.
But he moved theologically and politically to the right. Pope Paul VI named him bishop of Munich in 1977 and appointed him a cardinal within three months. Taking the chief doctrinal job at the Vatican in 1981, he moved with vigor to quash liberation theology in Latin America, cracked down on liberal theologians and in 2000 wrote the Vatican document ‘‘Dominus Jesus,’’ asserting the truth of Catholic belief over others.
Benedict also faced questioning by some critics about what he and others have said was his conscription into the Hitler Youth and the German army during the Nazi era. He was also faced accusations that he displayed reticence and insensitivity about the Holocaust.
In a book-length interview in 1997, Benedict said, ‘‘As a seminarian, I was registered in the Hitler Youth.’’ He added, ‘‘As soon as I was out of the seminary, I never went back.’’ As pope he visited Auschwitz in 2006 as a gesture of atonement, calling himself a ‘‘son of the German people.’’
Benedict ‘‘centered his papacy on giving faith to Christians, focusing on the essence of what it means to be a Christian, and he managed to do it in spite of the fact that his communicative capacities weren’t so brilliant,’’ the Vatican expert Sandro Magister said. ‘‘Most common people, I don’t mean intellectuals, saw him as a disinterested man who spent all his life for a high cause, which was to revive the faith.’’
In Rome, where souvenir shops often carry more postcards of John Paul than of Benedict, news of Benedict’s resignation was met with surprise and some sadness.
‘'Anyone could tell that he was old and sick, and that such a complicated situation like the one he has to face is a lot, but I had never heard that a pope could quit,’’ said Simonetta Piersanti, 52, a cleaning woman in a residence run by nuns.
She mentioned a common Roman saying, ‘‘When a pope dies, they just elect another,’’ which captures the lack of excitement with which Italians greet historic events. ‘‘We'll have to do it even without the death part,’’ she added.
Alan Cowell contributed reporting from London and Elisabetta Povoledo from Rome.