On 17 August, French heavy howitzers battered Les Lilas and Mondovi blockhouses all day and by nightfall both strong points had been breached and the garrisons captured. The bag of prisoners taken since 16 August was more than with fifteen guns. From the southern edge of the inundations between Dixmude and Drie Grachten, the French line had been pushed forward to the west bank of the Steenbeek as far as the south end of St Janshoek. South of Mondovi blockhouse, the Steenbeek had been crossed and on the extreme right, the had swung northwards to the south bank of the Broombeek, eliminating the possibility of the Fifth Army being outflanked from the north. French engineers had worked in the swamps and morasses to repair roads, bridge streams and build wire entanglements, despite constant German artillery fire. The advance brought the French clear of the northern stretch of the (third position).