In the following March the Bohemian crown became vacant by the death of Matthias. On the 31st of July the Bohemian estates pronounced the formal deposition of Ferdinand, and on the 26th of August they elected as their king Frederick, elector palatine. The new king and his queen, Elizabeth of England, arrived in Bohemia in October, and were crowned somewhat later at St Vitus's cathedral in Prague. Warfare with Austria continued during this year--1619. Thurn occupied Moravia, which now threw in its lot with Bohemia, and he even advanced on Vienna, but was soon obliged to retreat. In the following year events took a fatal turn for Bohemia. The powerful duke Maximilian of Bavaria joined his forces to those of Ferdinand, who had become Matthias's successor as emperor, and who was determined to reconquer Bohemia. Ferdinand also received aid from Spain, Poland and several Italian states. Even the Lutheran elector of Saxony espoused his cause. A large imperialist army, under the command of the duke of Bavaria, Tilly and Bouquoi, entered Bohemia in September 1620. After several skirmishes, in all of which the Bohemians were defeated, the imperial forces arrived at the outskirts of Prague on the evening of the 7th of November. On the following morning they attacked the Bohemian army, which occupied a slightly fortified position on the plateau known as the "Bila Hora" (White Hill). The Bohemians were defeated after a struggle of only a few hours, and on the evening of battle the imperialists already occupied the port of Prague, situated on the left bank of the Vltava (Moldau). King Frederick, who had lost all courage, hurriedly left Prague on the following morning. Submission of Bohemia.