The Siege of Leuven was an important siege in the Thirty Years' War in which a Franco-Dutch army under Frederick Henry of Orange and the French Marshals Urbain de Maillé-Brezé and Gaspard III de Coligny, who had invaded the Spanish Netherlands from two sides, laid siege to the city of Leuven, defended by a force of 4,000 comprising local citizen and student militias with Walloons, Germans, Spanish and Irish of the Army of Flanders under Anthonie Schetz, Baron of Grobbendonck. Wikipedia