In 1538 Guelders fell to William of Jülich, Cleves and Berg During that period the great town fire of 1540 occurred on 21 June of that year. The fire broke out during a summer heatwave, almost entirely razing the town apart from few houses by the Brück Gate and on "Maarstraße". Help came from the neighbouring Guelders towns of Roermond and Venlo. Emperor Charles V who, in 1543, following the capture of Düren and Julich during his march on Roermond with a 30,000 strong army, stayed personally in Erkelenz. ended the Guelders succession wars at the Treaty of Venlo. The town now ended up, together with the Duchy of Guelders, under to the Spanish House of Habsburg and was part of the Spanish Netherlands, then the richest country in Europe. So, for example, the town was able, as the inscription on a rock near the entrance testifies, to replace the destroyed town hall as early as 1546 with a new building that is still standing.