In spring and summer 1572 many cities in the Low Countries came under control of William of Orange, some actively supporting the rebels, other taking a more cautious attitude. Mechelen had opened its gates to the troops of William on August 31. William continued his advance towards Mons, but left a garrison in Mechelen under command of Bernard van Merode. On September 21 William was forced by a large Spanish army under the Duke of Alba to withdraw to Holland. The Duke of Alba now wanted to retake all cities in the South and decided to set an example. He ordered his son Fadrique Álvarez de Toledo to punish Mechelen for tolerating a rebel garrison. Plundering this rich city would also calm his troops, which hadn't received any pay in a long time.