John reigned from 1958-1963 and is a hero to liberal Catholics for having convened the Second Vatican Council. The meetings brought the church into the modern era by allowing Mass to be celebrated in local languages rather than Latin and encouraged greater dialogue with people of other faiths, particularly Jews.
During his globe-trotting, quarter-century papacy, John Paul II helped topple communism and invigorated a new generation of Catholics, while his defense of core church teaching on abortion, marriage and other hot-button issues heartened conservatives after the turbulent 1960s.
Benedict was one of John Paul's closest confidantes and went on to preside over a deeply tradition-minded eight-year papacy. His successor Francis seems a pope much more inspired by the pastoral, simple style of the "good pope" John.
Yet Francis offered each new saint heartfelt praise in his homily, saying John had allowed himself to be led by God to call the council, and hailing John Paul's focus on the family. It's an issue that Francis has asked the church as a whole to take up for discussion with a two-year debate starting this fall.
"They were priests, bishops and popes of the 20th century," Francis said. "They lived through the tragic events of that century, but they were not overwhelmed by them."
Benedict put John Paul on the fast-track for possible sainthood just weeks after his 2005 death, responding to the chants of "Santo Subito!" or "Sainthood Now!" that erupted during his funeral Mass. John Paul's canonization is now the fastest in modern times.
John's sainthood run, on the other hand, languished after his 2000 beatification. Rather than let John Paul have the limelight with a canonization on his own — emboldening many in the conservative wing of the church — Francis decided to pair him up with John. To do so, Francis tweaked the Vatican's own saint-making rules, deciding that John could be made a saint alongside John Paul without the necessary second miracle usually required.
Francis sounded a note of continuity in his homily, praising John for having called the council and John Paul for helping implement it.
"John XXIII and John Paul II cooperated with the Holy Spirit in renewing and updating the church in keeping with her pristine features, those features which the saints have given her throughout the centuries," Francis said.
During the ceremony, Francis took a deep breath and paused for a moment before reciting the saint-making formula in Latin, as if moved by the history he was about to make in canonizing two popes at once.
As soon as he did so, applause broke out from a crowd in St. Peter's and beyond.
"This is such a historic moment," marveled the Rev. Victor Perez, who brought a group of students from the John Paul High School in Houston, Texas and waited for nearly 12 hours to get near St. Peter's. "John Paul was so impactful on the church. He completed the work of Vatican II. Today honors the last 50 years of what God has done in the church."
In John Paul's native Poland, bells rang out as soon as Francis pronounced the two men saints.
"He changed Poland and he changed us with his teaching and with his visits here," an emotional Maria Jurek said as she watched the proceedings on giant TV screens at a sanctuary dedicated to John Paul in Krakow.
In the Philippines, where John Paul in 1995 drew the largest ever crowd for a papal Mass at 4 million, Filipinos watched the canonization on TV and joined local celebrations, including a suburban Manila parade of children dressed like the pope.