MUNICH -- As campuses across Europe and America boiled with unrest in 1968, an intellectual star at one of Germany's most prestigious universities, the Rev. Joseph Ratzinger, saw the school's militant student movement turn on him with all its force.
A group of University of Tübingen students hell-bent on sacking the political and especially religious establishment of postwar Germany staged a wave of protests to disrupt the Catholic priest's lectures. One professor remembers a Marxist student shouting at one point, ''We want to destroy you!"
Despite the disruption, Ratzinger did not confront the student demonstrators, according to fellow professors who recounted the events of that time, nor did he feel the need for dialogue with them, as did many other young professors.
Instead, Ratzinger decided to leave Tübingen and in 1969 withdrew to his native, predominantly Catholic Bavaria to anchor the theology department at a more conservative university in Regensburg.
For those who know the man who has become Benedict XVI and who will be formally installed as pope at a two-hour Mass today, his response to the turmoil of 1968 was a turning point in his intellectual life that captured the essence of a man whose answer to conflict and hostility has been to seek contemplation and study, rather than confrontation or dialogue with those unwilling to listen.
To supporters, this tendency to retreat reflects a quiet strength, a moral compass, that will guide the new pope. To his detractors, it exemplifies a conservative intransigence toward the modern world that they fear will take the church in the wrong direction.
But supporters and detractors alike -- from fellow priests and neighbors in his hometown in Bavaria to those who have worked closely with him in academia and at the Vatican -- see turning inward as a defining pattern throughout the 78 years of his life.
As a boy, with the horrors of World War II unfolding around him, Ratzinger withdrew into a preseminary school, where he discovered his passion for theology and buried himself in his religious studies.
In the 1970s, as the consumerism and secularization of modern Germany left Catholic churches largely empty on Sundays, he grew to believe that Catholics should withdraw from what he would later call ''the dictatorship of relativism" to find solace and quiet resistance in the true doctrine of the faith.
''Withdrawal is a theme that runs through his life, but withdrawal in a spiritual sense, in the sense of recollection, a retirement to the inner room of the soul, which in him is a place that is very rich," said the Rev. Joseph Augustine Di Noia, an American priest who is undersecretary of the Congregation for the Doctrine of the Faith. Di Noia worked closely with Ratzinger, who under Pope John Paul II headed the congregation for the last 24 years.
Di Noia said that Pope Benedict discussed this theme with him in a visit to his former office the day after he was elected to the papacy and explained how it figured in his choice of his papal name. He stressed that the name was inspired by St. Benedict, the sixth-century founder of the Benedictine monasteries. Confronted with the collapse from within of the Holy Roman Empire and the onslaught of the barbarians, St. Benedict withdrew to form hilltop monasteries devoted to the preservation of the church. Those monasteries spread over Europe and became the foundation of Christendom at the end of the Dark Ages .
''He sees in Saint Benedict and the monasteries he created a model for forming local communities that are vibrant, but not accommodating to the ambient culture," Di Noia said.
Coming of age amid war
Joseph Ratzinger was born in April 1927 in Marktl am Inn, the youngest of three children. His father, Georg, was a policeman in the small village at the foothills of the Bavarian Alps.
When he was 10, the family moved to the outskirts of Traunstein, the larger Bavarian town, to be near St. Michael's, a religious boarding school, where Joseph and his older brother, Georg, were to receive a Catholic foundation that their parents hoped would lead to the priesthood. Germany's National Socialist movement was tightening its grip on power and the father, also named Georg, took early retirement from the police force, which was becoming an instrument of Nazi control over society.
''My father was one who with unfailing clairvoyance saw that a victory of Hitler's would not be a victory for Germany, but rather a victory of the Antichrist that would surely usher in apocalyptic times for all believers, and not only for them," Ratzinger wrote in ''Milestones: Memoirs 1927-1977."
The Catholic Church was increasingly pushed toward accommodation of the Nazi government's demands. In 1941, when Hitler passed a law making membership in the Hitler Youth obligatory, all of the students at St. Michael's had to join. A very few resisted, including Rupert Berger, who was later ordained with Ratzinger and whose father was a known leader of the resistance.
But Joseph and his brother, Georg, joined the Hitler Youth. The Rev. Josef Grabmaier, 78, who attended primary school and seminary with the Ratzinger brothers, said the boys would be called to line up and salute the Führer. He said he often stood in the straight rows with one or both Ratzingers, listening to local Nazi Party officials lecture them for hours.
Grabmaier, who is an admirer of Ratzinger and said he was thrilled by his election as pope, said in an interview in his parish office that Ratzinger and his family never sympathized with the Nazis, and that they were all simply caught in the grip of a totalitarian state.
In his memoirs, Ratzinger wrote that he was able to avoid many of the Hitler Youth obligations. ''Thank goodness, there was a very understanding mathematics teacher," he wrote. ''He himself was a Nazi but an honest man, who said to me, 'Just go once and get the document so that we have it.' When he saw that I simply didn't want to, he said, 'I understand, I'll take care of it,' and so I was able to stay free of it."
John L. Allen Jr., Vatican correspondent for the National Catholic Reporter, wrote in ''Cardinal Ratzinger: The Vatican's Enforcer of the Faith," published in 2000: ''The way Ratzinger describes his Traunstein experience today, it sounds as if most of the political chaos and the war was 'out there,' while he was reading great literature, playing Mozart, joining his family on trips to Salzburg, and poring over Latin conjugations. The truth, however, is that the horrors of the Reich were right there in Traunstein, staring Ratzinger in the face."
Bert Zeiser, 75, who grew up across the road from the Ratzingers, confirmed this impression. He said the young Joseph was absorbed in his studies, emerging from the family home only occasionally and then with his head buried in one of his theology texts. He did not march in the Hitler Youth parades in town.
''The only parade I ever saw was with his family," Zeiser said. ''They would march to church in a strict formation, with his father in the lead, the two brothers flanking him, and the sister and mother trailing behind. The father was very strict, even mean."
In 1943, at the age of 16, Ratzinger and his entire class were drafted into the German military. They were assigned as ''flak helpers," the boys who helped man antiaircraft positions. Ratzinger told Time magazine in 1993 that because of a badly infected finger during this time, he never learned to fire a gun, and his own weapon was never loaded.
In September 1944, he was sent to the border between Austria and Hungary. As the German Army collapsed in late April 1945, just before the May 8 German surrender, he returned to his home. The American military moved into Traunstein in the following weeks, and a tank division took a position just outside the family home. Ratzinger was briefly taken prisoner of war and released a few weeks later.
In the fall of 1945, Ratzinger entered the seminary at St. Michael's in Traunstein. He was ordained in 1951. He served briefly as an auxiliary priest in a few parishes, but quickly delved into what he felt was his calling: academia.
Ratzinger began his graduate studies in philosophy at the University of Munich and received a doctorate in theology from Freising. He was known by fellow priests studying with him as shy and introverted, but also urbane and cultured, mastering eight languages, including German, English, French, Italian, Portuguese, and Spanish.
His was a reformist but traditionally grounded voice during the Second Vatican Council, when the church became more open under Pope John XXIII. His work at the council focused on undoing church laws on heresy which harkened back to the Middle Ages.
During the council sessions, he first met another intellectual rising star of the church, the Rev. Hans Küng, a Swiss-born scholar who later recruited Ratzinger in 1966 to come to Eberhard-Karls University at Tübingen. Ratzinger accepted, but amid the tumult of the late 1960s he began to shed his reformist spirit. When the Marxist students began invading his classes, Ratzinger's conservative tendencies were emboldened.
''He was for the first time in his life really directly confronted," said Küng in a telephone interview last week. He said the campus upheaval came from German students who blamed their parents' generation for the rise of Nazism and sought to topple any remnant of traditional German institutions. Leftist extremists sparked a wave of bombings and slayings across the country.
In a 1997 interview in the book, ''Salt of the Earth," Ratzinger described such political ideologies as ''tyrannical, brutal, and cruel."
''That experience made it clear to me that the abuse of the faith had to be resisted," he wrote.
Küng said: ''Our reaction was very different. He walked away. He just was not prepared or not willing to talk to those who spoke from emotion. I physically defended my microphone in the lecture hall. I didn't like what the Marxists were saying at all, but I was willing to listen, to at least try to hear what they had to say.
''This is the negative side of the man, the intolerant side," said Küng, who in subsequent years had a legendary battle with Ratzinger over Catholic teaching and resisted his attempt to bring him before the Congregation for the Doctrine of the Faith, the body once known as the Inquisition.
Küng said he was ''enormously disappointed" to learn that his onetime colleague was the new successor to St. Peter. He accused Ratzinger of a ''pattern of persecution" of academics and theologians in Europe and America, several of whom have lost teaching positions or been prevented from publishing.
In 1969, Ratzinger left Tübingen and returned to Bavaria, which today remains a region of small, rural Catholic hamlets steeped in political and religious conservatism. He returned here to the company of his brother, who was conducting the choir at Regensburg, and his sister and took a teaching position at the University of Regensburg.
The Rev. Joseph Fessio -- a professor at Ave Maria University, a conservative Catholic institution in Florida -- was drawn to Ratzinger's teaching back then, and in 1972 studied under him. ''He doesn't only have gravitas; he also has levitas, or lightness," said Fessio, who now runs a publishing house that has printed most of Ratzinger's writing in English. ''He is inspiring and brilliant."
From Munich to the Vatican
In 1977, Ratzinger was plucked from academia and became archbishop of Munich and Freising and the same year was elevated to cardinal by Pope Paul VI.
He was an inspiring manager who ''listened attentively" to staff and ''allowed them to be creative," said Winfried Roehmel, longtime director of the press office for the Munich Archdiocese. But, Roehmel conceded, ''he didn't love the administrative aspect of the job."
Ratzinger frequently retreated to the Bavarian countryside, enjoying his beloved white sausages and Bavarian sweets and visiting with his brother either in Regensburg or in a special apartment provided for them at their old seminary, St. Michael's.
After John Paul II assumed the papacy in 1978, he sought someone who could help him centralize church authority in the Vatican and move toward more conservative teachings. John Paul saw Ratzinger as his man and in 1981 appointed him prefect of the Congregation for the Doctrine of the Faith. He held that position until this month.
In the last five years, Ratzinger worked closely with the congregation undersecretary, Di Noia, who said Ratzinger's image as a strict enforcer was an ''entirely false" impression. He could be ''very demanding," but always inspiring.
''There was no one who enjoyed the esteem of his colleagues more than Cardinal Ratzinger," Di Noia said. ''He is a listener, an inspiring leader who sees his role in the congregation and now in the papacy to reevangelize and reinvigorate Catholicism."
Even Küng, his most persistent critic, said that he believed that Ratzinger is a brilliant man who in his opening statement as pope seemed to be expressing an effort toward reconciliation.
''We must wait and see, but experience shows that the enormous weight of the papacy can change people, even Joseph Ratzinger," Küng said.
Globe correspondents Aliza Marcus and Martina Taubenberger contributed to this report.