his sincerity in taking this step; it was not an act of pure opportunism.  His early Catholicism had probably been little more than an outward profession, and as soon as he began to think seriously about religious questions, his natural bent had led him first to the Lutheran faith of his family, and then to the sterner doctrines, which had gained so firm a foothold in the towns of Holland and Zeeland.  Nevertheless William, though henceforth a consistent Calvinist, was remarkable among his contemporaries for the principles of religious toleration he both inculcated and practised.  He was constitutionally averse to religious persecution in any form, and by the zealots of his party he was denounced as lukewarm; but throughout his life he upheld the right of the individual, who was peaceful and law-abiding, to liberty of opinion and freedom of worship.

The year 1574 opened favourably.  By a remarkable feat of arms the veteran Spanish commander Mondragon had, October, 1572, reconquered several of the Zeeland islands.  His men on one occasion at ebb-tide marched across the channel which lies between South Beveland and the mainland, the water reaching up to their necks.  The patriot forces had since then recovered much of the lost ground, but Middelburg was strongly held, and so long as the Spaniards had command of the sea, was the key to the possession of Zeeland.  On January 29, 1574, the Sea-Beggars under Boisot attacked the Spanish fleet near Roemerswaal and after a bloody encounter gained a complete victory.  The siege of Middelburg was now pressed and Mondragon surrendered, February 18.  The prince at once set to work to create a patriot government in the province.  Four towns had representatives, Middelburg, Zierikzee, Veere and Flushing.  William himself acquired by purchase the marquisate of Flushing and thus was able to exercise a preponderating influence in the Provincial Estates, all of whose members were required to be Calvinists and supporters of the rebel cause.

The investment of Leyden by the Spaniards threatened however, now that Haarlem had fallen, to isolate South Holland and Zeeland; and William did not feel himself strong enough to make any serious attempt to raise the siege.  Lewis of Nassau therefore, with the help of French money, set himself to work with his usual enthusiastic energy to collect a force in the Rhineland with which to invade the Netherlands from the east and effect a diversion.  At the head of 7000 foot and 3000 horse—­half-disciplined troops, partly Huguenot volunteers, partly German mercenaries—­he tried to cross the Meuse above Maestricht with the intention of effecting a junction with the Prince of Orange.  He was accompanied by John and Henry of Nassau, his brothers, and Christopher, son of the Elector Palatine.  He found his course blocked by a Spanish force under the command of Sancho d’Avila and Mondragon.  The encounter took place on the heath of Mook (April 14) and ended in the crushing defeat of the invaders.  Lewis and