At last the general discontent took shape in open resistance. The success of the French Huguenots in wresting the free exercise of their faith from the monarchy told on the Calvinists of the Low Countries. The nobles gathered in leagues. Riots broke out in the towns. The churches were sacked, and heretic preachers preached in the open fields to multitudes who carried weapons to protect them. If Philip's system was to continue it must be by force of arms, and the king seized the disturbances as a pretext for dealing a blow he had long meditated at the growing heresy of this portion of his dominions. Pius the Fifth pressed him to deal with heresy by the sword, and in 1567 an army of ten thousand men gathered in Italy under the Duke of Alva for a march on the Low Countries. Had Alva reached the Netherlands while Mary was still in the flush of her success, it is hard to see how England could have been saved. But again Fortune proved Elizabeth's friend. The passion of Mary shattered the hopes of Catholicism, and at the moment when Alva led his troops over the Alps Mary passed a prisoner within the walls of Lochleven. Alone however the Duke was a mighty danger: nor could any event have been more embarrassing to Elizabeth than his arrival in the Netherlands in the autumn of 1567. The terror he inspired hushed all thought of resistance. The towns were occupied. The heretics were burned. The greatest nobles were sent to the block or driven, like William of Orange, from the country. The Netherlands lay at Philip's feet; and Alva's army lowered like a thundercloud over the Protestant West. [Sidenote: Mary's abdication.]