Beginning in the spring of 1917, three Catholic shepherd children living near Fatima reported apparitions of an Angel, and starting in May of 1917, apparitions of the Virgin Mary, whom the children described as the Lady of Fátima. The children reported a prophecy that prayer would lead to an end to the Great War, and that on October 13th of that year the Lady would reveal her identity and perform a miracle "so that all may believe." Newspapers reported the prophesies, and many pilgrims began visiting the area. The children's accounts were deeply controversial, drawing intense criticism from both local secular and religious authorities. A provisional administrator briefly took the children into custody, believing the prophecies were politically motivated in opposition to the officially secular First Portuguese Republic established in 1910.
Estimates of the number of people present range from 30,000 and 40,000, by Avelino de Almeida writing for the Portuguese newspaper O Século, to 100,000, estimated by lawyer Dr. José Almeida Garrett, the son of a professor of natural sciences at the University of Coimbra.
Fr Andrew Pinsent, research director of the Ian Ramsey Centre for Science and Religion at Oxford University, states that "a scientific perspective does not rule out miracles, and the event at Fatima is, in the view of many, particularly credible." He states that a usual prejudice involves a lack of understanding of the scope of scientific laws, which merely describe how natural systems behave isolated from free agents. Concluding that the event is "a public miracle of the most extraordinary kind and credibility", he sees the year of the event, as connected to significant historical milestones that call for Fatima's message of repentance: Protestantism in 1517, Freemasonry in 1717 and Atheistic Communism in 1917.