When Pope Leo XIV signed off on the excommunication of four newly consecrated bishops and other formal followers of the Society of Saint Pius X on July 2, the dark cloud of schism floated over Christianity’s largest religious denomination. Leo, only in office since last year, invoked the extraordinary measure in the first big public test for the first American pontiff.

Whether the faithful rally around the smart and apparently amiable man who sits on the throne of St Peter or draw back from the move will determine the immediate trajectory of the former Robert Prevost, of Chicago, who over the last year has emerged as a world leader unafraid to speak truth to power. Leo has famously stood up to President Donald Trump and Vice President J. D. Vance on immigration, the war in Iran, and Catholic doctrine.

Declaring a group “in schism” is rare, meaning it is no longer considered inside the church. A memorable schism was the Protestant Reformation, five hundred years ago.