Election of Pope Saint Leo I, 45th successor of Peter whose pontificate lasted 21 years. He is called the "Leo the Great" because of his energetic work in maintaining the unity of the Church. He called the 4th and 5th Ecumenical Councils and defined the mystery of the Incarnation. But the one thing he is most remembered for is turning away the dreaded Attila the Hun - the "Scourge of God" at the gates of Rome through Divine intervention.
Cardinal Lando is chosen to be the antipope Innocent III during the legitimate reign of Pope Alexander III. Lando was chosen to succeed the second of three antipopes Callistus III who died a year earlier. Alexander conquered Innocent and confined him to a the Benedictine Abbey of SS. Trinita of La Cava in Salerno for life where he died of old age.
Cardinal Maffeo Barberini is chosen as Pope Urban VIII, 235th successor of Peter. He carried out the work on the sacred texts - the Pontifical and the Breviary. Galileo Galilei was condemned during his pontificate. His papacy lasted 21 years.
Pope Pius XI issues his 23rd encyclical Acerba animi dealing with the persecution of the Church in Mexico.
Pope Pius XI ushers his final encylical - his 30th on the Rosary Ingravescentibus malis.
Pope Paul VI reconvenes the Second Vatican Council, opening the second session in Rome.
Pope Paul VI calls the first Bishops Synod worldwide that would last for exactly one month.