Mercurius became Pope John II, making him the first pope to change their name after attaining popehood.
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Pope Innocent III brought together the council for the Fourth Council of the Lateran, which was held at the Lateran Palace in Rome, Italy.
Pope Innocent IX was elected.
Pope Fabian succeeded Anterus and became the twentieth pope of Rome.
The first Vatican Council, also known as Vatican I, decrees the doctrine of Papal infallibility.
Pope Constantine died.
