In 1799 Chasteler was appointed Generalquartiermeister (chief of staff) to Suvorov and commander of a wing of the Austrian army in Italy. Serving at the Battle of Cassano 27 April, he invested Tortona in May, but was wounded at Alessandria, 16 July. Elevated to Commander of the Order of Maria Theresa and made chief of staff in Southern Germany in 1800, he serving at Engen and Mösskirch, before leading a Brigade in the Tyrol, distinguishing himself at the action of Scharnitz.