In 1917, the Blessed Virgin Mary appeared to three children at Fatima, Portugal six times on the 13th day of each month from May until October. In these remarkable apparitions, Our Lady detailed in ways these children could understand what would happen to the Church and the world in the 20th Century.
She foretold the end of World War I.
She warned that unless men repented and turned their hearts toward God, and ceased offending God and disrespecting the Mother of God, a far worse war would break out-World War II.
She instructed the children and all believers to pray the rosary "for the conversion of sinners and of Russia." If Russia were not consecrated to her, she warned, Russia would continue to spread her errors throughout the world and persecute the Church until this consecrating occurred. The Blessed Virgin was foretelling the rise of Soviet Communism, which began that November.
We now know that Our Lady also foretold an assassination attempt upon a Pope. In 1981, Pope John Paul II was nearly killed by the Turk Ali Acga-he survived, and placed the bullet from the assassination attempt into the crown on the statue of the Blessed Virgin at Fatima. John Paul consecrated not only Russia but the world to the Immaculate Heart of Mary.
Ten years later, the Soviet Union collapsed.
The Church in no way requires the faithful to believe in private apparitions such as the one that many believe occurred in Portugal in 1917. In 1930, the Bishop of Fatima declared the apparitions to be "worthy of belief."
I believe they happened.