May 23, 1430: French mystic and military hero Joan of Arc is captured by the Burgundians. They sold her to English, who tried her for sorcery and heresy (see issue 30: Women in the Medieval Church).
May 23, 1498: Italian reformer Girolamo Savonarola, who preached aggressively against the corruption of northern Italy's church and society, is hanged for heresy and his body burned. After gaining fame for successful prophecies, he sought to establish an ascetic Christian community. Scholars still debate whether he was a saintly prophet or a fanatic.
May 23, 1533: Thomas Cranmer, archbishop of Canterbury, declares King Henry VIII's marriage to Catherine of Aragon null and void: a key moment in the English Reformation (see issue 48: Thomas Cranmer).
May 23, 1618: Bohemian Protestant rebels storm the castle of Catholic Hapsburg king Ferdinand II and throw his governors out the window (and into a pile of manure). This act touched off Europe's Thirty Years War, which ended in 1648 by the Treaty of Westphalia (see issue 13: Jan Amos Comenius).
May 23, 1633: Though Huguenots (French Protestants) had tried to colonize "New France" (Canada) for three decades, France declares only Roman Catholics are allowed to permanently settle there (see issue 71: The Huguenots).