The preaching of the crusade had its effect in the summer, when the besiegers were joined by reinforcements from Brabant, Flanders and Artois. In the autumn, a West Frisian contingent arrived and encamped on the eastern side of the city, completing the investment. These Frisians, subjects of William as count of Holland, had taken vows to join the crusade of Louis IX to the Holy Land, but these had been commuted to allow them to join the crusade against Frederick II instead.