The siege was made possible by the defeat of the French army at the Battle of Oudenarde and the landing in Ostend of large amounts of ammunition and food after the Battle of Wijnendale. For most of the campaign, Eugene commanded the forces besieging Lille, while Marlborough commanded the forces covering those forces against external French interference. For a short period in late September however, after Eugene was injured on the 21st, Marlborough took command of both the besiegers and the covering force.