May 20, 325: Emperor Constantine convenes the first Ecumenical Council in Nicaea (now Iznik), Bithynia, to discuss Arianism, a heresy arguing that Christ was subordinate to God the Father. "I entreat you," Constantine said at the opening of the Council of Nicea, "to remove the causes of dissension among you and to establish peace." The council attempted to resolve the bitter conflict by anathematizing Arius (Arianism's founder) and ordering the burning of all his books, but the conflict continued to rage for decades (see issue 51: Heresy in the Early Church).
May 20, 1277: Pope John XXI dies when his castle ceiling collapses on him. The name was a mistake—there was never a John XX.
May 20, 1506: Christopher Columbus, who saw himself as a missionary, not just an explorer, dies impoverished in Spain at age 55. "I hope in our Lord that it will be the greatest honor to Christianity that, unexpectedly, has ever come about," he concluded in the log of his first voyage to the Americas (see issue 35: Christopher Columbus).
May 20, 1690: John Eliot, English missionary to the Native Americans of New England and publisher of the first Bible printed in America, dies (see issue 41: The American Puritans).
May 20, 1960: Six months before John F. Kennedy, a Roman Catholic, is elected president of the United States, the Southern Baptist Convention condemns the election of Catholics to public office. "When a public official is inescapably bound by the dogma and demands of the church," it declared, "he cannot consistently separate himself from these.
May 29, 1453: Constantinople, capital of Roman Empire (and late Byzantine Empire) since Constantine founded the city in 324, falls to the Turks under Mehmed II, ending the Byzantine Empire. Muslims later rename the city Istanbul. The lavish cathedral that crowned the city, Hagia Sophia, was also converted into a mosque (see issue 74: Christians & Muslims). Today it is a museum and restoration work is being done to preserve both the Muslim and Christian layers of religious history.