The decision by Pope Leo XIV to excommunicate members of the Society of Saint Pius X (SSPX) is the latest twist in a long-running saga between the Vatican and this contentious traditionalist group. It is yet more evidence of the deep polarisation between conservatives and progressives within the Catholic church.

The Vatican issued a statement on July 2 to the effect that SSPX had “committed an act of a schismatic nature” by ordaining four bishops the previous day at a ceremony in Écône, the village in Switzerland where SSPX was founded in 1970.

The society was established and named after Pope Pius X by the controversial French archbishop Marcel Lefebvre. He was an adherent to the uncompromising positions Pius (who reigned from 1903 to 1914) held against “modernism” – the attempts by some Catholics to apply contemporary intellectual and moral trends to the teachings of the church.

In 1907, Pius X had declared modernism to be an attack on all elements of the church by those who “vaunt themselves as reformers”.

Those who joined the SSPX reacted specifically to reforms brought about within the church by the Second Vatican Council (often known as Vatican II).

Convened between 1962 and ’65, Vatican II was reportedly described by Pope John XXIII as an attempt to “open the windows and let in the fresh air”. It sought to recognise the rapidly shifting world of the 20th century, and reaffirm the role of the church in........

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