Joseph Ratzinger never hid the fact he thought the Roman Catholic papacy was too big for one man.
For several days after being elected in 2005, Pope Benedict - as he chose to be called - spoke as if in shock. At his first public Mass, he asked: "I must assume this enormous task, which truly exceeds all human capacity. How can I do this?"
At a meeting with fellow Germans the following day, Benedict surprised his well-wishers by likening the experience of being elected in the Sistine Chapel to getting dizzy as he watched a guillotine blade fall upon him.
Now he has broken six centuries of tradition and resigned, the Catholic Church is asking whether in an era of democracy, 24/7 television and Twitter, the papacy modeled on Renaissance-era monarchy is suffering the same fate. There have been sexual abuse scandals, disputes with Muslims and Jews, suspected money-laundering at the Vatican Bank and communications gaffes. Stacks of private files stolen by Benedict's own butler have documented corruption and in-fighting among senior officials.
Benedict hands on a 2,000-year-old institution whose reputation is tarnished, whose teaching is challenged by an increasingly secular world and whose priests struggle to minister to its growing population. The man who leads the world's largest church must be a spiritual guide for millions, an inspiration for the oppressed and the manager of a squabbling, dysfunctional Vatican bureaucracy.
"No sane man seeks the burden of the papacy," says George Weigel, a prominent Catholic theologian in Washington D.C. "It is by definition impossible, because it asks a man to take up a burden of leadership that no human being can possibly attract by his own powers."
The challenge for the cardinals due to enter the conclave next week is to seize the chance to face up to the problems and identify reforms that help the next pope address them. The job of leading the estimated 1.2 billion Catholics around the world must be done by one man.
Thomas Reese, a Jesuit scholar and author of "Inside the Vatican", puts it simply: "What they are looking for is Jesus Christ with an MBA."
WHAT WENT WRONG
To get to the root of the Church's problems, some look back before Benedict's papacy to 1978, when, after a turbulent period, Pope John Paul mounted the throne of St. Peter to reassert orthodox Catholic doctrine and Vatican authority.
The then-Cardinal Ratzinger was doctrinal watchdog for a vigorous papacy which stifled discussion on questions such as the role of women in the Church or issues concerning human sexuality.
That problem will be highlighted by one man's absence from the conclave. Last week, Scotland's Cardinal Keith O'Brien joined the ranks of clergy exposed for sexual abuse over past decades when he stepped down as archbishop of Edinburgh. Younger priests had complained he had behaved inappropriately with them in the 1980s. He has since apologized for sexual conduct "below the standards expected of me".
Benedict dealt with sexual abuse cases in the final years of John Paul's papacy, and when he became Pope, he started out boldly. He ordered Rev Marcial Maciel, founder of the strict Legionaries of Christ order and a favorite of his predecessor, to retire to a monastery in penance for his secret life as father of several children, sexual abuser of seminarians and drug user.
He apologized for the scandals and made private meetings with abuse victims a regular part of his visits abroad.
COVER-UPS
But the dirt kept surfacing. Four official reports into clerical child abuse in Ireland in as many years exposed details of priestly sin, and how the hierarchy covered it up. One clearly said the Vatican was complicit, leading to a once-unthinkable rebuke by Prime Minister Enda Kenny. Dublin's embassy to the Holy See was closed in late 2011 and relations remain strained.
Between December 2009 and April 2010, three Irish bishops resigned and apologized for mishandling abuse cases in their dioceses. Also in 2010, a German bishop quit and apologized for physically abusing children. A Belgian bishop stepped down after admitting having molested his own under-age nephews. A Chilean bishop accused of abusing an altar boy quit in 2012, saying he had committed "an imprudent act" but the boy was not underage.
Such "zero tolerance" did not always apply to bishops who protected the predators in their dioceses. Cardinal Roger Mahony of Los Angeles stayed in office for years despite accusations - later proven true - that he shielded molesting clerics from the police. He has admitted to making "mistakes" and said he had been naïve about the impact of abuse. Bishop Robert Finn still leads the Kansas City diocese after being convicted of failing to alert authorities to a trove of child pornography found on a priest's computer. He apologized "for the hurt that these events have caused".
In these and other cases, the pattern was that the Church acted only under pressure, and resisted calls to punish bishops who had mismanaged them. Catholics who see politicians shamed over sex scandals and executives fired for mismanagement asked why Church decision-makers should not be held responsible.
"We long for the day when Church officials announce that this cardinal or this bishop is being demoted because ... Church officials want to clean things up," said David Clohessy, head of the Survivors Network of those Abused by Priests.
No centralized figures exist to gauge the impact of this abuse on Church revenues but in the United States, a study in 2006 by the Center for Applied Research in the Apostolate at Georgetown University (CARA) in Washington showed Catholics became less generous towards their dioceses after 2002, the year the scandals broke.
In a sign they mistrusted their bishops, Catholics continued contributing overall, but gave more to their parishes or charities independent of their dioceses, said Mary Gautier, senior research associate.
From 2005-2011, the Church has incurred more than $2.3 billion in costs related to settlements for abuse, CARA has said.
In Germany, some 180,000 people left the Catholic Church in 2010, a 40 percent jump over the previous year, after sexual abuse allegations exploded there that year. The rate fell back to 127,000 - around the normal level of those leaving for financial or other reasons - the following year.
RETREAT FROM RELIGION
The abuse is not the only reason Catholics have turned their backs on the Church. A more general retreat from organized religion perplexes leaders who grew up in societies where the Church had deep influence.
The drift is most marked in Europe, Catholicism's traditional heartland. Eight years after Cardinal Ratzinger chose the papal name Benedict in honor of Europe's patron saint, vocations, baptisms and marriages in churches are still declining.
The trend has political consequences. Governments and courts have ignored Church objections and legalized same-sex unions or marriage, and insisted that Catholic adoption agencies help gay couples find a child.
Even in heavily Catholic Poland, politicians are proposing a clearer separation between church and state. The mayor of the southern city of Czestochowa, whose monastery and golden-haloed Black Madonna painting attract millions of pilgrims yearly, wants to offer couples the option of in vitro fertility treatment, firmly opposed by the Church.
Bishops in Europe and North America have begun defending Church teachings more forcefully against such political pressures. In the Philippines, the only country in Asia with a Catholic majority, secularist trends have reached the point where Manila passed a family planning law despite stiff Church opposition.
ROLE FOR WOMEN
In the Chicago suburb of Evanston, lawyer Lynne Mapes-Riordan is already preparing for change, studying for a leadership role which the Church does not now allow. "I hope they will open this to women someday," says the 50-year-old mother of two. "I don't have any particular insight as to when that might be."
This stained-glass ceiling for women is increasingly out of step in a world where they do every job from soldier to CEO, German Chancellor Angela Merkel is the most powerful politician in Europe and even some Muslim countries have had female prime ministers.
Many say the Church cannot operate without women because they pass on the faith as mothers and religious educators. Yet in the traditionalist atmosphere Benedict fostered, small advances like girl altar servers at Mass are being rolled back. Even women who do not advocate female ordination - something the Vatican completely rules out - question what place the Church has for them and their daughters.
Surveys in the United States show Catholic women under 30 are now less religious than men their age: some 45 percent attend Mass once a year or less, compared with 39 percent of men.
When asked in an Indiana University study if they had complete confidence in religious organizations, 16 percent of the men said yes. None of the women did.
Sister Patricia Wittberg, a sociologist who did the study using data from 2002-8, said this was the first generation of American Catholic women who were less religious than men. "That, in my opinion, is extremely ominous," she said. "Who's going to baptize the kids?"
CONSERVATIVE AFRICA
The new pope will also be under pressure to bring the Church leadership to terms with a massive shift in its centre of gravity.
Around 68 percent of the world Catholic population is now in Latin America, Africa and Asia, but that is not reflected at the Vatican. Europe will still have 61 cardinals among the 115 electors in the conclave while the developing world will have only 39 - about 34 percent of the total.
These "Global South" Catholics are far from a bloc. Each area has its own focus and juggling different regional priorities requires the skill of a seasoned diplomat.
Sub-Saharan Africa was the faith's fastest growing region by far over the past century, soaring to 16 percent of the world Catholic population in 2010 from only one percent in 1910. And African Catholics are much more conservative than "inclusive" Catholics in the north.
"Africa stands strongly by Catholic beliefs," said Rev Isaac Achi, whose church near the Nigerian capital Abuja lost 44 parishioners when a Boko Haram Islamist extremist drove a car packed with explosives into it on Christmas Day 2011. "We fight against abortion, we fight against homosexuals, lesbians and contraception."
Thousands of miles to the east, in Luwero, Uganda, mechanic Kizito Emmanuel, 38, agrees. "We don't want any change," he said. "Family planning doesn't need these pills. I don't support priests getting married. As an ordinary Catholic, the biggest challenge I face is a problem of capital."
PRACTICAL PROTESTANTS
Poverty haunts many Latin American congregations, too, but the Church's main challenges there are the deep inroads made by evangelical and Pentecostal churches into what was once a Catholic bastion. These Protestant churches offer livelier services, practical help for the poor and an upbeat message more attuned to the continent's growing economies than the sacrifice that Catholics are taught to endure.
The numbers quitting the Catholic Church have been dramatic. In Brazil, the largest Catholic country in the world, just over 65 percent of the population is Catholic now, a steep drop from the 92 percent recorded in 1970.
Miriam Vargas Nunes, 35, a mother of two from Niteroi near Rio de Janeiro, left the Church a decade ago after visiting a Baptist church with friends. "I felt more welcome than I ever did in a Catholic Mass," she said. In Argentina, Claudia Valenzuela, 26, joined an evangelical Bible study group two months ago after losing her job and finding nobody at her Catholic Church to console her.
Much of this change has come with the migration of rural workers to big cities and the drift shows up among U.S. Latino communities as well. A Gallup poll last year tracked Catholics at 54 percent and falling, and Protestants at 28 percent. Latinos with no religion rose to 15 percent from 11 percent in 2008.
A CLERICAL CLIFF
There is also an increasingly urgent shortage of priests, particularly in Western countries; so many are near or beyond retirement age that the Church faces a 'clerical cliff' there. Catholicism is centered on sacraments, especially the eucharist at Mass, that only ordained men can administer. Without priests, local churches or parishes cannot operate.
The ranks of the clergy in Europe and North America began to thin out in the late 1960s as discontented priests left and fewer men entered the priesthood. Those who stayed are dying off and new vocations are not sufficient to replace them. In the United States, for example, there were 58,632 priests in 1965 and only 38,964 last year.
Ireland, once a major exporter of priests, saw only six ordinations while 55 priests died in 2010. Poland was the only European country with positive figures, showing 516 ordinations to 285 deaths. But even there, the deaths are accelerating while the ordinations slow down. Even in Africa, a boom in new priests is not keeping up with growth in the Catholic population.
This means a growing workload. Priests often have to serve more than one parish to make up for missing colleagues. Parishes are being regrouped into larger units to share staff. In Latin America, where there is only one priest for more than 7,000 Catholics compared with one for every 1,500 in Europe, the shortage is cited as one reason so many have found evangelical movements more welcoming.
CURING THE CURIA
Inside the Vatican, the new pope will have to face up to the Curia, a centuries-old bureaucracy dominated by Italian clerics, which can make or break a papacy because it can block or delay papal projects.
Most cardinals outlining their priorities for the future put "governance" or "reform of the Curia" high on their list, saying other reforms can flow from that.
The "Vatileaks" scandal last year showed corruption and in-fighting at high levels, and the Curia is not known for efficiency in its ranks. At the Vatican, which spawned the modern term "nepotism" because Renaissance popes gave jobs to their unqualified nephews ("nipote" in Italian), hiring is not always on merit.
The Curia's influence within the Church is surprising, because it has only about 2,000 staff, and they usually leave work in the early afternoon. There are no cabinet meetings, and internal coordination between the departments - allocated such tasks as upholding Catholic doctrine, naming new saints, or promoting Christian unity - is patchy. A serene atmosphere of old-world courtesy prevails.
Weigel, the U.S. theologian, has named a series of reforms a determined pope could make, including introducing a 40-hour work week, turning the staff from an Italian fiefdom to a truly international team, and creating an executive staff for the pontiff. But no structural reform will work, he said, if the staff just have a manager's mentality rather than seeing themselves as missionaries working for the pope.
"The Curia is still deeply influenced by Italianate work habits and that's problematic," he said. "If you look at the rest of this society, it doesn't happen to be functioning very well."