ROME — The Italian capital is bracing for the arrival of more than 2 million pilgrims to help celebrate the formal declaration that John XXIII and John Paul II — perhaps the two most beloved popes of modern times — will be declared saints.
Sunday's date has been marked on the calendar of devout Catholics since it was announced last September by Pope Francis, whose own popularity rivals that of the two soon-to-be saints barely a year into his papacy.
The massive influx, fueled in part by 1,700 buses, 60 flights and a half-dozen special trains for pilgrims from John Paul's native Poland, is likely to be the largest gathering in Rome since John Paul's funeral eight years ago.
"John XXIII and John Paul II were so revered by both Catholics and non-Catholics that it is expected that shining a light on them in this way will help draw people together," said the Rev. Alistair Sear, a retired church historian who met both popes.
"The two popes appeal to different segments of the church, which means Sunday should be a moment of unity and good feeling for a church that can use it."
John became pope in 1958 and convened the Second Vatican Council, which tried to make the Mass and liturgy of the 2,000-year-old church more accessible to the 20th century. He died in 1963, and his legacy included rifts among churchgoers who felt he was too liberal in his revamping of church rituals.
John Paul, who was Polish and at the time was the first non-Italian pope in more than 400 years, became pope in 1978 and is considered one of the more charismatic popes in recent times.
He survived an assassination attempt in 1981 to become a major figure in the Cold War that pitted democratic countries against the communist dictatorship that was the Soviet Union. His own Poland was a captive of the state for decades.
John Paul urged nations to confront the Soviet Union as an evil empire that denied the most basic of rights, including that of freedom of religion. He notably apologized for the Roman Catholic Church having imprisoned Galileo in seeking to portray the church as not hostile to science, and apologized to Jews for the history of Christian anti-Semitism, said Holly Grieco, associate professor of religious studies at Siena College in Loudonville, N.Y.
He also re-emphasized the Catholic church's opposition to abortion and the taking of all life, and was a favorite among Catholic youth, attracting millions to his World Youth Day gatherings.
"John Paul II was also known for his concern for the poor and vulnerable," Grieco said.
But he also was criticized for being too conservative, and victims of sexual abuse by priests say he should've done more to bring the abusers to justice.
John Paul II's biographer, George Weigel, told National Review Online that "it's clear that the Holy See and the pope were not living the abuse crisis in 'real time' with the church in the United States."
But he said John Paul did eventually move to reform seminaries to try to ensure an end to the molestation cases of earlier years that first came to light under his papacy.
Michael Anthony Novak, assistant professor of theology at Saint Leo University in Saint Leo, Fla., says that the two popes are arguably the most notable leaders of the church in the 20th century. In the case of John, he pointed out that there was great promise in modern thought and encouraged bishops to speak their minds about it and thus loosened the centralizing tendencies of the Vatican's bureaucracy.
"This sparked a wave of re-energized engagement by the church with the rest of the world, which has continued to this day," Novak said.
There are those who say the church is ill-served by making popes into saints — a relatively new phenomenon — given that saints are church figures held up as examples of the way Christians should try to live their lives.
"Saints are supposed to be models of sanctity for Christians to imitate, but who can a pope be a model for except for another pope?" asked the Rev. Thomas Reese of the National Catholic Reporter.
But the faithful see the event as a landmark moment for the church.
"It will be a wonderful moment to focus on what brings Christians together," said Angela Conti, 71, a church volunteer in Rome. "With The Good Pope (John XXIII's nickname), John Paul and Francis all in the spotlight, it will bring many people to tears."
Carmelo Orlando, 55, a limousine driver, agreed: "I am not the only one who expects to remember this day for the rest of his life."
Joining them in the crowd will be as many as 50 heads of state or government and official national delegations from more than 100 countries, plus as many as 150 cardinals, 1,000 bishops and delegations from several dozen non-Catholic faiths. The U.S. delegation will be led by presidential adviser John Podesta.
"It's an event of global significance that will draw attention to Rome, and we have to be sure it goes off with no problems," said Rome mayor Ignazio Marino, who announced massive increases in the number of on-duty police and extra public transport.
Police said security for the event would be especially tight given Francis' penchant for breaking with protocol and unexpectedly mixing with large crowds.