After receiving reinforcements provided by Archduke Albert, his campaign of 1619 did much to reverse the fortunes of the war. On 10 June he defeated Ernst von Mansfeld in the Battle of Sablat, thereby forcing the Bohemians to abandon their siege of Budweis. He also commanded the imperial forces during the Battle of White Mountain on 8 November 1620. As a result of his successes, Emperor Ferdinand II gave him estates at Nové Hrady, Rožmberk and Libějovice. These estates remained in the family until 1945. Bucquoy was killed during the siege of Érsekújvár (Neuhäusel) (Nové Zámky) on 10 July 1621. One of his commanders, Torquato Conti attempted to retrieve his body from the battlefield but was captured. Conti was later released and replaced Bucquoy as a commander of Imperial forces. His funeral, with full honours, took place in the Franciscan Church, Vienna, on 31 July 1621.