A great battle took place on the 17th of August between the two land armies at Mons-en-Puelle (or, Mont-en-Pevele, according to the true local spelling), near Lille; the action was for some time indecisive, and even after it was over both sides hesitated about claiming the victory; but when the Flemings saw their camp swept off and rifled, and when they no longer found in it, say the chroniclers, "their fine stuffs of Bruges and Ypres, their wines of Rochelle, their beers of Cambrai, and their cheeses of Bethune," they declared that they would return to their hearths; and their leaders, unable to restrain them, were obliged to shut themselves up in Lille, whither Philip, who had himself retired at first to Arras, came to besiege them.

When the first days of downheartedness were over, and at sight of the danger which threatened Lille and the remains of the Flemish army assembled within its walls, all Flanders rushed to arms.

"The labors of the workshop and the field were everywhere suspended," say contemporary Historians: "the women kept guard in the towns: you might traverse the country without meeting a single man, for they were all in the camp at Courtrai, to the number of twelve hundred thousand, according to popular exaggeration, swearing one to another that they would rather die fighting than live in slavery." Philip was astounded.

"I thought the Flemings," said he, "were destroyed; but they seem to rain from heaven; "and he resumed his protestations and pacific overtures.

Circumstances were favorable to him: old Guy de Dampierre was dead; Robert of Bethune, his eldest son and successor, was still the prisoner of Philip the Handsome, who set him at liberty after having imposed conditions upon him.