Instead of advancing on Thourout and beyond, it had to dig itself in on a line of defence from Rawlinson's left at Zonnebeke to Bixschoote, where the French began their own and the Belgian front along the Yser to Nieuport. The impact of the opposing forces had flattened them out until they extended to the coast, and the point at which they reached it remained fixed for four years to a day.
On the 15th the Belgians captured Thourout and the British Menin, crossing the Lys at various points and taking Comines on the 16th. The effect of this advance was to precipitate a comprehensive German retreat both north and south.
The Germans were firmly held on a line running from south of Ostend to Thourout, Roulers and Menin, the last mentioned place being on the border north of Lille. Flanking attacks being no longer possible, as the western flanks of both armies rested on the North Sea, the Germans were compelled to make a frontal assault along the line formed by the Belgian frontier.
Trenches, sections of broken roads, familiar to them from above, crossed and recrossed each other under them, and they descried to the north of Langemarck road the railway, or what used to be the railway, between Ypres and Thourout and the Saint-Julien-Poelkapelle road.
Haig's 1st Corps was expected shortly to fill the gap between Rawlinson's 4th and D'Urbal, and Rawlinson was instructed to advance on the 18th, seize Menin, and then await Haig, who was to move through Ypres on to Thourout, Bruges, and Ghent.
Pieces of money from the ports of Sluis and Duurstede have been found in both countries, and the frequency of intercourse with the North was such that a monastery was established at Thourout, near Duurstede, for the special purpose of training missionaries for the conversion of the Danish traders.