Pope Francis joined tens of thousands of faithful in bidding farewell to Benedict XVI at a rare requiem Mass Thursday for a dead pope presided over by a living one, ending an unprecedented decade for the Catholic Church that was sparked by the German theologian's decision to retire.

Bells tolled and the crowd applauded as pallbearers carried Benedict's cypress coffin out of the fog-shrouded St. Peter's Basilica and placed it before the altar in the square outside. Wearing the crimson vestments typical of papal funerals, Francis opened the service with a prayer and closed it by solemnly blessing the simple casket — decorated only with the former pope's coat of arms.

In between, Francis made only fleeting reference to Benedict in his homily, offering a meditation on Christ instead of a eulogy of his predecessor's legacy before the casket was sealed and entombed in the basilica grotto.

Heads of state and royalty, clergy from around the world and thousands of regular people flocked to the subdued ceremony, despite Benedict's request for simplicity and official efforts to keep the first funeral for a pope emeritus in modern times low-key.

Many mourners hailed from Benedict's native Bavaria and donned traditional dress, including boiled wool coats to guard against the morning chill.

"We came to pay homage to Benedict and wanted to be here today to say goodbye," said Raymond Mainar, who traveled from a small village east of Munich for the funeral. "He was a very good pope."

Ignoring exhortations for decorum at the end, some in the crowd held banners or shouted "Santo Subito!" — "Sainthood Now!" — echoing the spontaneous chants that erupted during St. John Paul II's 2005 funeral.

The former Joseph Ratzinger, who died Dec. 31 at age 95, is considered one of the 20th century's greatest theologians and spent his lifetime upholding church doctrine. But he will go down in history for a singular, revolutionary act that changed the future of the papacy: He retired, the first pope in six centuries to do so.

Francis has praised Benedict's courage in stepping aside, saying it "opened the door" for other popes to do the same.

Some 50,000 people attended Thursday's Mass, according to the Vatican, after around 200,000 paid their respects during three days of public viewing.

Only Italy and Germany were invited to send official delegations, but other leaders took the Vatican up on its offer and came in their "private capacity." They included several heads of state, at least four prime ministers and two delegations of royal representatives. In addition, a host of patriarchs joined 125 cardinals in the seats to the side of the altar, and the Russian Orthodox Church sent its foreign envoy.

Among those attending was Hong Kong Cardinal Joseph Zen, who was given special court permission to attend the funeral. Zen was detained in May on suspicion of colluding with foreign forces under China's national security law after he fell afoul of authorities over his participation in a now-silenced democracy movement. His passport was revoked when he was detained.

Benedict's close confidants were also in attendance, and the former pope's longtime secretary, Archbishop Georg Gaenswein, bent down and kissed a book of the Gospels that was left open on the coffin before the ceremony began.

Matteo Colonna, a 20-year-old seminarian from Teramo, Italy, said he came in part because of the historic nature of the funeral — but also because it had personal resonance for him.

"The first spark of my vocation started under the pontificate of Benedict, but then it became even stronger under Pope Francis," Colonna said, while sitting in prayer in St. Peter's Square at dawn. "I see a continuity between these two popes and the fact that today Francis is celebrating the funeral in Benedict's memory is an historical event."

But the service was also significant for what it lacked: the feeling of uncertainty that would normally accompany the passing of a pope before a new one is elected. Instead, with Francis in place, Benedict's death marked the end of a decade in which a reigning pope lived alongside a retired one.

"Benedict has been the bridge between John Paul and Francis," said Alessandra Aprea, a 56-year-old from Meta di Sorrento near Naples. "We could not have Francis without him."

Early Thursday the Vatican released the official history of Benedict's life, a short document in Latin that was placed in a metal cylinder in his coffin before it was sealed, along with the coins and medallions minted during his papacy and his pallium stoles.

The document gave ample attention to Benedict's historic resignation and referred to him as "pope emeritus," citing verbatim the Latin words he uttered on Feb. 11, 2013, when he announced he would retire.

The document, known as a "rogito" or deed, also cited his theological and papal legacy, including his outreach to Anglicans and Jews and his efforts to combat clergy sexual abuse "continually calling the church to conversion, prayer, penance and purification."

Francis didn't mention Benedict's specific legacy in his homily and only uttered his name once, in the final line, delivering instead a meditation on Jesus' willingness to entrust himself to God's will.

"Holding fast to the Lord's last words and to the witness of his entire life, we too, as an ecclesial community, want to follow in his steps and to commend our brother into the hands of the Father," Francis said.

During St. John Paul II's quarter-century as pope, Ratzinger spearheaded a crackdown on dissent as prefect of the Congregation for the Doctrine of the Faith, taking action against the left-leaning liberation theology that spread in Latin America in the 1970s and against dissenting theologians and nuns who didn't toe the Vatican's hard line on matters like sexual morals.

His legacy was marred by the clergy sexual abuse crisis, even though he recognized earlier than most the "filth" of priests who raped children, and actually laid the groundwork for the Holy See to punish them.

As cardinal and pope, he passed sweeping church legislation that resulted in 848 priests being defrocked from 2004 to 2014, roughly his pontificate with a year on either end. But abuse survivors still held him responsible, for failing to sanction any bishop who moved abusers around, refusing to mandate the reporting of sex crimes to police and identifying him as embodying the clerical system that long protected the institution over victims.

Mike McDonnell of the U.S. abuse survivor group SNAP said while Benedict passed new canon laws, he could have done far more to influence John Paul to take firm action. Referring to Benedict's nickname as "God's Rottweiler," he said: "In our in our view, it was a dog bark without a bite. Certainly he could have done more."

A group representing German clergy abuse survivors called on German officials attending Benedict's funeral to demand more action from the Vatican on sexual abuse. Eckiger Tisch asked leaders to demand that Francis issue a "universal church law" stipulating zero tolerance in dealing with abuse by clergy.

The funeral ritual itself is modeled on the code used for dead popes but with some modifications given Benedict was not a reigning pontiff when he died.

After the Mass, Benedict's cypress coffin was placed inside a zinc one, then an outer oak casket before being entombed in the crypt in the grottoes underneath St. Peter's Basilica that once held the John Paul's tomb before it was moved upstairs.

While Thursday's Mass was unusual, it does have some precedent: In 1802, Pope Pius VII presided over the funeral in St. Peter's of his predecessor, Pius VI, who had died in exile in France in 1799 as a prisoner of Napoleon.