Pope Francis on Friday directly reversed a signature liturgical decision of Pope Benedict XVI, moving to strongly limit use of the old Latin Mass and spurring anger from church traditionalists.

The pope, whose tenure has been characterized by deep church divisions and conservative opposition, said in a letter that his new ruling was a step “in defense of the unity of the Body of Christ.” He suggested that those who favored the old Latin Mass had been exploiting the rite as a way to “reinforce the divergences, and encourage disagreements that injure the Church.”

Francis’s move will not change church services for the majority of the world’s 1.3 billion Catholics, who are largely familiar with the modern Mass — shaped amid church reforms of the 1960s — that is recited in the local language, not Latin.

But many traditionalists remain champions of the old Latin Mass, a liturgy that dates back more than a millennium and has become a central point in church divisions in the wake of the Second Vatican Council, which ended in 1965.

Francis’s decision was remarkable, if only because he was taking a major step into the church’s liturgical wars and essentially erasing the decision of his conservative predecessor, Pope Emeritus Benedict XVI, who continues to live inside the Vatican’s walls. In 2007, Benedict removed a rule requiring a local bishop’s permission to celebrate the old Latin Mass. Francis not only reinstated that rule but added other restrictions.

In dioceses where groups celebrate the old rite, also known as the Tridentine Mass, bishops must also work to determine that the celebrants “do not deny the validity and the legitimacy” of the Second Vatican Council, which helped shape many church reforms. Among those changes were the popularization of Mass in the vernacular, making worship more accessible to regular Catholics.

In a letter accompanying his decision, Francis said he was “saddened” that the use of the old Latin Mass often doubles as a rejection of the Second Vatican Council, under the argument that its reforms “betrayed” the church’s true traditions. But Francis said that to doubt the council is to “doubt the Holy Spirit himself.”

“The great issue for the Catholic Church has always been the question of change,” said David Gibson, director of Fordham University’s Center on Religion and Culture. The old Latin Mass had become “a wedge issue, to divide, to elevate one part of the church as superior to other parts of the church,” Gibson said. “And that is intolerable.”

In the Latin Mass, the priest often faces away from the congregation. The rite also includes the use of particular — often elaborate — vestments.

Francis’s decision, coming just two days after he was discharged from the hospital after colon surgery, takes effect immediately. It angered church conservatives, who have long opposed other aspects of Francis’s papacy. They accuse him of watering down church traditions and paying more attention to cultural issues than church doctrine.

In a statement, Bill Donohue, the conservative president of the New York-based Catholic League, said that Francis’s restrictions “are designed to require its adherents to acknowledge the legitimacy of the reforms instituted by Vatican II in the 1960s.” He said the pope might be acting in fear that too many Catholics preferred the old Latin Mass.

“This is likely to lead to more ‘Mass shopping,’ rather than less,” Donohue said. “The Latin Mass has been especially popular with young Catholics, and it is too late to stop them from finding parishes that will allow it to continue.”

Roberto de Mattei, president of the conservative Lepanto Foundation in Rome, said that the old Latin Mass held great appeal because traditionalists think it does not just “commemorate” Jesus’ sacrifice, but also makes it present — while conveying to worshipers “the idea of a holy mystery, pronounced in Latin, which is the sacred language of the church.”

De Mattei said Francis’s action was akin to a “declaration of war” against the church’s own traditions.

“He’s stepping away, distancing himself, not from traditionalist groups or movements, but against an endless tradition of popes, saints and doctors of the church,” de Mattei said.