When Pope John XXIII announced the creation of the Second Vatican Council (also known as Vatican II) in January 1959, it shocked the world. There hadn't been an ecumenical council — an assembly of Roman Catholic religious leaders meant to settle doctrinal issues — in nearly 100 years.
"Many people maintained that with the definition of papal infallibility in 1870, councils were no longer needed. So it was a big surprise," Georgetown University professor Rev. John W. O'Malley says.