Philip consulted his constable, Walter de Chatillon, who had served the kings his predecessors in their wars against Flanders.
"Whoso hath good stomach for fight," answered the constable, "findeth all times seasonable." "Well, then," said the king, embracing him, "whoso loveth me will follow me." The war thus resolved upon was forthwith begun.

Philip, on arriving with his army before Cassel, found the place defended by sixteen thousand Flemings under the command of Nicholas Zannequin, the richest of the burghers of Furnes, and already renowned for his zeal in the insurrection against the count.

For several days the French remained inactive around the mountain on which Cassel is built, and which the knights, mounted on iron-clad horses, were unable to scale.
The Flemings had planted on a tower of Cassel a flag carrying a cock, with this inscription:-- "When the cock that is hereon shall crow, The foundling king herein shall go." They called Philip the foundling king because he had no business to expect to be king.

Philip in his wrath gave up to fire and pillage the outskirts of the place.

The Flemings marshalled at the top of the mountain made no movement.