Why is Vatican II so Significant in the Modern Church? Vatican II was the 21st ecumenical council recognized by the Roman Catholic church, which became the symbol of the church's openness to the modern world. The council was announced by Pope John XXIII on January 25, 1959, and held 178 meetings in the autumn of each of four successive years. The first gathering was on October 11, 1962, and the last on December 8, 1965. Of 2908 bishops and others eligible to attend, 2540 from all parts of the world participated in the opening meeting. The U.S. delegation of 241 members was second in size only to that of Italy. Asian and African bishops played a prominent role