At the outset of the War of the Fifth Coalition, Gyulay led the IX Armeekorps in Archduke John's army in Italy. As originally organized, the corps consisted of three divisions under Franz Gorup von Bessanez, Christian Wolfskeel von Reichenberg, and Vinzenz Knesevich von Saint Helena. Gyulay commanded 22,290 infantry, 2,400 cavalry, and 86 artillery pieces. The IX Armeekorps fought at the Battle of Sacile on 16 April 1809. During the fighting, the surprise intervention of the IX Armeekorps on the right flank was important in securing the Austrian victory over the Franco-Italian army of Eugène de Beauharnais. His brother Albert led VIII Armeekorps in the same battle.