As hundreds of thousands of Catholic pilgrims descended upon Cologne, Germany, yesterday for Pope Benedict XVI’s first appearance on the world stage, the pontiff sailed down the Rhine to address throngs of young followers, sounding the themes that, according to observers, will signal the course of his nascent papacy.

Benedict, returning to his home country for the first time since ascending to the throne of St. Peter in April, said yesterday that he felt “deep joy” upon arriving in Germany for World Youth Day, Britain’s Daily Telegraph reported. The celebration – initiated in 1985 by John Paul II – is considered the first major test of Benedict’s pastoral abilities.

Four months have passed since Benedict was elected to the papacy, amid fears that he would make radical changes to the church. Yet those close to the pontiff said yesterday that the pope has dedicated himself to being a guardian of both the legacy of his predecessor and the traditions of the Roman Catholic Church.

“I think we’ve all noticed in the few months that he’s been pope is that he’s very anxious to continue all that was good in the years of Pope John Paul II,” the archbishop of New York, Edward Cardinal Egan, told The New York Sun earlier this week before departing for Cologne.

“He’s tried to handle things in a step-by-step, careful, prudent manner, and I think he’s succeeded in that,” Cardinal Egan said. Part of this approach, he said, stemmed from Benedict’s personality: Over the course of his interactions with then-Cardinal Ratzinger, Cardinal Egan said, he found the future pontiff to be “measured, prudent, and thoughtful.”

John Paul’s handpicked biographer and a senior fellow of the Ethics and Public Policy Center in Washington, D.C., George Weigel, said yesterday that Benedict’s business-as-usual approach was a function of the church itself. “The Catholic Church does not reinvent itself every time there’s a new pope – because the pope is not the inventor of a tradition, he’s the servant of a tradition.”

Benedict’s early pontificate has been marked by subtle adjustments at the Vatican. For example, he is likely to modify the process by which bishops are chosen, Mr. Weigel said, adding that the pontiff has conducted surprisingly thorough reviews of the dossiers of those nominated. “He’s clearly taking in hand, in a very personal way, this very urgent matter,” Mr. Weigel said.

“During the second Vatican Council, Joseph Ratzinger was very concerned that the office of bishop in particular was becoming a bureaucratic function within the church rather than the office of an apostle, and I suspect he’s going to address that,” he added.

In terms of the church’s leadership at the highest levels, Benedict has kept in the Roman Curia – a kind of cabinet most of John Paul II’s staff. Benedict did replace himself as head of the church’s Congregation for the Doctrine of the Faith with the archbishop of San Francisco, William Levada, in a nod to America’s growing influence within the church.

An American cleric at the Congregation of the Doctrine of the Faith, the Reverend Augustine DiNoia, however, said that next month will bring more significant changes. The pontiff will seek to replace those in “Cabinet-level” positions, Rev. DiNoia, who worked with then-Cardinal Ratzinger at the CDF, said, responding to anticipated vacancies resulting from the current staff’s age and a desire to leave a mark on the curia.

In the meantime, according to Catholic News Service, the pontiff has vacationed at his Alpine retreat and at the papal villa in Castel Gandolfo, completing a book begun three years ago. Vatican spokesmen have declined to reveal the work’s subject.

The pontiff’s most anticipated project is his first encyclical, a formal document on doctrine issued by the pope to bishops, expected in the fall. One likely topic of the encyclical, Mr. Weigel said, could be “the challenge of Europe.” Indeed, the elevation of a European to the throne of St. Peter has been considered an indication that the church was making a bid for the hearts and minds of a continent thought to be given over to secularism, and even the selection of his papal name – Benedict is the patron saint of Europe – was taken as a sign that the new pontiff was intent on rejuvenating the faith of his home continent.

Saving Europe was a theme touched upon by the pontiff yesterday, according to the Telegraph, which reported that Benedict urged young Catholics to evangelize and welcomed non-Catholics to share in Europe’s Christian heritage. Observers yesterday said it was consistent with Benedict’s belief that the Catholic laity, particularly young people, would be instrumental in restoring faith to Europe.

This weekend’s appearances at World Youth Day will mark a turning point in Benedict’s papacy, insofar as the summer lull has given the pontiff a chance to prepare for the fall, when he is expected to clearly define his pontificate.

Despite the quietude, however, Benedict’s tenure has not been without its share of flaps.

In May, the editor of America magazine, a New York-based Jesuit publication that had come under fire from the Vatican for its occasional embrace of unorthodox views, the Reverend Thomas Reese, resigned amid allegations that he had been forced out by Cardinal Ratzinger when he was still head of the Congregation of the Doctrine of the Faith. A July op-ed in the New York Times by the archbishop of Vienna, Christoph Cardinal Schonborn, raised eyebrows when the cardinal took issue with precepts of evolutionary theory. Even the appearance of an old letter, written by then-Cardinal Ratzinger in 2003 containing concerns about the “seductions” of Harry Potter, became fodder for a firestorm.

Still, Benedict has changed the minds of critics. “He has come off as a lot less doctrinaire than a lot of people feared he would be in public,” an associate editor of America Magazine, the Reverend James Martin, said yesterday.

Perhaps the most visible public-relations quandary came, however, in late July, when the pope denounced acts of Islamist terror in several countries without naming Israel.

This episode notwithstanding, the pope has generally received high marks from Jewish leaders. Benedict’s ecumenism has also won over Eastern Orthodox leaders. Reconciliation with those churches was the central theme of a papal visit to Bari, Italy.

Despite being 78, Rev. DiNoia said that those in Rome have observed nothing but joy from Benedict since he became pope. Reports out of Cologne yesterday suggested that the pontiff was further buoyed by the presence of hundreds of thousands of young people, whom Benedict will lead throughout the weekend, culminating in an open-air Mass on Sunday expected to draw nearly 1 million.

“He’s taken to the job like a fish to water,” Rev. DiNoia said.