Answer: Pope John XXIII opened the Second Vatican Council on October 11, 1962, marking the first ecumenical council of the Catholic Church in ninety-two years. More than 2,000 bishops gathered in Rome to discuss how the Church could better present its teachings and engage with the modern world. The council would continue until 1965 and become one of the most influential events in modern Catholic history.

During the opening ceremonies, Pope John XXIII delivered his famous address, Gaudet Mater Ecclesia ("Mother Church Rejoices"), encouraging the bishops to approach the future with hope rather than pessimism. The reforms and teachings that emerged from Vatican II affected Catholic worship, ecumenical relations, and the Church's relationship with contemporary society, leaving a lasting impact that is still felt today.