In 1570 Tsar Ivan IV of Russia installed Duke Magnus as King of Livonia. The other forces opposed this appointment. The Livonian Order saw no other way than to seek protection from Sigismund II Augustus (King of Poland and Grand Duke of Lithuania), who had intervened in a war between Bishop William of Riga and the Brothers in 1557. After coming to an agreement with Sigismund II Augustus and his representatives (especially Mikołaj "the Black" Radziwiłł), the last Livonian Master, Gotthard Kettler, secularized the Order and converted to Lutheranism. In the southern part of the Brothers' lands he set up the Duchy of Courland and Semigallia for his family. Most of the remaining lands were seized by the Grand Duchy of Lithuania. Denmark and Sweden re-occupied the north of Estonia.