his control. By 1303, another castle had been constructed for defense. In 1356, the Counts Palatine were granted far-reaching rights in the Golden Bull, in addition to becoming Electors. In 1386, Heidelberg University was founded by Rupert I, Elector Palatine.
Heidelberg University played a leading part in the era of humanism and reformation and the conflict between Lutheranism and Calvinism in the 15th and 16th centuries. Heidelberg's library, founded in 1421, is the oldest public library in Germany still intact. A few months after the proclamation of the 95 Theses, in April 1518, Martin Luther was received in Heidelberg, to defend them. In 1537, the castle located further up the mountain was destroyed in a gunpowder explosion. The duke's palace was built at the site of the lower castle.
In November 1619, the royal crown of Bohemia was offered to the Elector, Frederick V. (He was married to Elizabeth, eldest daughter of James I and VI of England and Scotland). He became known as the "winter king", as he reigned for only one winter before the Imperial House of Habsburg regained the crown by force. This overthrow in 1621 marked the beginning of the Thirty Years' War. In 1622, after a siege of two months, the armies of the Catholic League, commanded by Johann Tserclaes, Count of Tilly, captured Heidelberg. He gave the famous Bibliotheca Palatina from the Church of the Holy Spirit to the Pope as a present. The Catholic Bavarian branch of the House of Wittelsbach gained control over the Palatinate and the title of Prince-Elector. In 1648, at the end of the war, Frederick V's son Charles I Louis, Elector Palatine, was able to recover his titles and lands.
Urbain de Maill�-Br�z� fought in many battles. He also participated in the Siege of La Rochelle (1627�1628). In 1635 he conquered Heidelberg and Speyer, together with Jacques-Nompar de Caumont, duc de la Force, at the head of the Army of Germany.
To strengthen his dynasty, Frederick arranged
