After the National Convention of the French Republic had declared war on the Dutch Republic in February 1793, William was appointed commander-in-chief of the veldleger (mobile army) of the States Army (his father remained the nominal head of the armed forces). As such he commanded the troops that took part in the Flanders Campaign of 1793–95. He took part in the Battles of Veurne and Menin (where his brother was wounded) in 1793, and commanded during the Siege of Landrecies (1794), whose fortress surrendered to him. In May 1794 he had replaced general Kaunitz as commander of the combined Austro-Dutch forces on the instigation of Emperor Francis II who apparently had a high opinion of him. William was victorious at the Battles of Gosselies and Lambusart and proved to be an able commander, but the French armies ultimately proved too strong, and the general allied leadership too inept. Despite a well-executed attack by William on the French left, the allied army under Coburg was finally defeated at the Battle of Fleurus. The French first entered Dutch Brabant which they dominated after the Battle of Boxtel. When in the winter of 1794–95 the rivers in the Rhine delta froze over, the French breached the southern Hollandic Water Line and the situation became militarily untenable. In many places Dutch revolutionaries took over the local government. After the Batavian Revolution in Amsterdam on 18 January 1795 the stadtholder decided to flee to Britain, and his sons accompanied him. (On this last day in Holland his father relieved William honorably of his commands). The next day the Batavian Republic was proclaimed.
After the National Convention of the French Republic had declared war on the Dutch Republic in February 1793 William was appointed commander-in-chief of the veldleger (mobile army) of the States Army (his father remained the nominal head of the armed forces) As such he commanded the troops that took part in the Flanders Campaign of 1793–95 He took part in the Battles of Veurne and Menin (where his brother was wounded) in 1793 and commanded during the Siege of Landrecies (1794) whose fortress surrendered to him In May 1794 he had replaced general Kaunitz as commander of the combined Austro-Dutch forces on the instigation of Emperor Francis II who apparently had a high opinion of him William was victorious at the Battles of Gosselies and Lambusart and proved to be an able commander but the French armies ultimately proved too strong and the general allied leadership too inept Despite a well-executed attack by William on the French left the allied army under Coburg was finally defeated at the Battle of Fleurus The French first entered Dutch Brabant which they dominated after the Battle of Boxtel When in the winter of 1794–95 the rivers in the Rhine delta froze over the French breached the southern Hollandic Water Line and the situation became militarily untenable In many places Dutch revolutionaries took over the local government After the Batavian Revolution in Amsterdam on 18 January 1795 the stadtholder decided to flee to Britain and his sons accompanied him (On this last day in Holland his father relieved William honorably of his commands) The next day the Batavian Republic was proclaimed