It was believed in Ypres that the town had been saved by the intercession of the Virgin Mary, its patron saint. In the Cathedral Church of St. Martin the citizens set up an image of Notre Dame-de-Thuine, that is, Our Lady of the Enclosures, an allusion to the strong barrier of thorns which had kept the enemy at bay; and a kermesse, appointed to be held on the first Sunday of August every year in commemoration of the siege, received the name of the 'Thuindag,' or Day of the Enclosures.[14] The people of Ypres, though they fought on the French side, had good reason to be proud of the way in which they defended their homes; but the consequences of the siege were disastrous, for the commerce of the town never recovered the loss of the large working-class population which left it at that time.
The religious troubles of the sixteenth century left their mark on Ypres as well as on the rest of Flanders. Everyone has read the glowing sentences in which the historian of the Dutch Republic describes the Cathedral of Antwerp, and tells how it was wrecked by the reformers during the image-breaking in the summer of 1566. What happened on the banks of the Scheldt appeals most to the imagination; but all over Flanders the statues and the shrines, the pictures and the stores of ecclesiastical wealth, with which piety, or superstition, or penitence had enriched so many churches and religious houses, became the objects of popular fury. There had been field-preaching near Ypres as early as 1562.[15] Other parts of West Flanders had been visited by the apostles of the New Learning, and on August 15, 1566, the reformers swept down upon Ypres and sacked the churches.
In the awful tragedy which soon followed, when Parma came upon the scene, that 'spectacle of human energy, human suffering, and human strength to suffer, such as has not often been displayed upon the stage of the world's events', the town had its share of the persecutions and exactions which followed the march of the Spanish soldiery; but for more than ten years a majority of the burghers adhered to the cause of Philip. In July, 1578, however, Ypres fell into the hands of the Protestants, and became their headquarters in West Flanders. Five years later Alexander of Parma besieged it. The siege lasted until April of the following year, when the Protestants, worn out by famine, capitulated, and the town was occupied by the Spaniards, who 'resorted to instant measures for cleansing a place which had been so long in the hands of the infidels, and, as the first step towards this purification, the bodies of many heretics who had been buried for years were taken from their graves and publicly hanged in their coffins. All living adherents to the Reformed religion were instantly expelled from the place.'[15] By this time the population was reduced to 5,000 souls, and the fortifications were a heap of ruins.