With the siege of Ostend underway, Maurice then went on the offensive on the Rhine frontier in the summer of 1600. Rheinberg and Meurs were thus retaken from the Spanish yet again, although an attempt on s'Hertogenbosch failed during the winter months. At Ostend in January 1602 after being reinforced, Vere faced a huge Spanish assault organised by the Archduke and in bitter fighting this was repelled with heavy losses. Vere left the city soon after and joined Maurice in the field, while Albert was replaced by Ambrogio Spinola. The siege there dragged on for another two years as the Spanish attempted to take Ostend's strongpoints in a costly war of attrition. Around the same time Maurice continued his campaign, Grave was retaken but Vere was severely wounded during the siege. An attempt by the Dutch and English to relieve Ostend took place in mid-1604 but the inland of port of Sluis was besieged and captured instead. Soon after the Ostend garrison finally surrendered, after a siege of nearly four years and costing thousands of lives – for the Spanish, it was a pyrrhic victory.