As soon as the frost broke up Count Bossu, who had been building a fleet of small vessels in Amsterdam, cut a breach through the dyke and entered the lake, thus entirely cutting off communications. The Prince of Orange on his part was building ships at the other end of the lake, and was doing all in his power for the relief of the city. He was anxiously waiting the arrival of troops from Germany or France, and doing his best with such volunteers as he could raise. These, however, were not numerous; for the Dutch, although ready to fight to the death for the defence of their own cities and families, had not yet acquired a national spirit, and all the efforts of the prince failed to induce them to combine for any general object.
His principal aim now was to cut the road along the dyke which connected Amsterdam with the country round it. Could he succeed in doing this, Amsterdam would be as completely cut off as was Haarlem, and that city, as well as the Spanish army, would speedily be starved out. Alva himself was fully aware of this danger, and wrote to the king: "Since I came into this world I have never been in such anxiety. If they should succeed in cutting off communication along the dykes we should have to raise the siege of Haarlem, to surrender, hands crossed, or to starve."
The prince, unable to gather sufficient men for this attempt, sent orders to Sonoy, who commanded the small army in the north of Holland, to attack the dyke between the Diemar Lake and the Y, to open the sluices, and break through the dyke, by which means much of the country round Haarlem would be flooded. Sonoy crossed the Y in boats, seized the dyke, opened the sluices, and began the work of cutting it through. Leaving his men so engaged, Sonoy went to Edam to fetch up reinforcements. While he was away a large force from Amsterdam came up, some marching along the causeway and some in boats.
A fierce contest took place, the contending parties fighting partly in boats, partly on the slippery causeway, that was wide enough but for two men to stand abreast, partly in the water. But the number of the assailants was too great, and the Dutch, after fighting gallantly, lost heart and retired just as Sonoy, whose volunteers from Edam had refused to follow him, arrived alone in a little boat. He tried in vain to rally them, but was swept away by the rush of fugitives, many of whom were, however, able to gain their boats and make their retreat, thanks to the valour of John Haring of Horn, who took his station on the dyke, and, armed with sword and shield, actually kept in check a thousand of the enemy for a time long enough to have enabled the Dutch to rally had they been disposed to do so. But it was too late; and they had enough of fighting. However, he held his post until many had made good their retreat, and then, plunging into the sea, swam off to the boats and effected his escape. A braver feat of arms was never accomplished.
Some hundreds of the Dutch were killed or captured. All the prisoners were taken to the gibbets in the front of Haarlem, and hung, some by the neck and some by the heels, in view of their countrymen, while the head of one of their officers was thrown into the city. As usual this act of ferocity excited the citizens to similar acts. Two of the old board of magistrates belonging to the Spanish party, with several other persons, were hung, and the wife and daughter of one of them hunted into the water and drowned.
In the words of an historian, "Every man within and without Haarlem seemed inspired by a spirit of special and personal vengeance." Many, however, of the more gentle spirits were filled with horror at these barbarities and the perpetual carnage going on. Captain Curey, for example, one of the bravest officers of the garrison, who had been driven to take up arms by the sufferings of his countrymen, although he had naturally a horror of bloodshed, was subject to fits of melancholy at the contemplation of these horrors. Brave in the extreme, he led his men in every sortie, in every desperate struggle. Fighting without defensive armour he was always in the thick of the battle, and many of the Spaniards fell before his sword. On his return he invariably took to his bed, and lay ill from remorse and compunction till a fresh summons for action arrived, when, seized by a sort of frenzy, he rose and led his men to fresh conflicts.
On the 25th of March a sally was made by a thousand of the besieged. They drove in all the Spanish outposts, killed eight hundred of the enemy, burnt three hundred tents, and captured seven cannons, nine standards, and many wagon loads of provisions, all of which they succeeded in bringing into the city.
The Duke of Alva, who had gone through nearly sixty years of warfare, wrote to the king that "never was a place defended with such skill and bravery as Haarlem," and that "it was a war such as never before was seen or heard of in any land on earth." Three veteran Spanish regiments now reinforced the besiegers, having been sent from Italy to aid in overcoming the obstinate resistance of the city. But the interest of the inhabitants was now centred rather on the lake than upon the Spanish camp. It was from this alone that they could expect succour, and it now swarmed with the Dutch and Spanish vessels, between whom there were daily contests.
On the 28th of May the two fleets met in desperate fight. Admiral Bossu had a hundred ships, most of considerable size. Martin Brand, who commanded the Dutch, had a hundred and fifty, but of much smaller size. The ships grappled with each other, and for hours a furious contest raged. Several thousands of men were killed on both sides, but at length weight prevailed and the victory was decided in favour of the Spaniards. Twenty-two of the Dutch vessels were captured and the rest routed. The Spanish fleet now sailed towards Haarlem, landed their crews, and joined by a force from the army, captured the forts the Dutch had erected and had hitherto held on the shore of the lake, and through which their scanty supplies had hitherto been received.
From the walls of the city the inhabitants watched the conflict, and a wail of despair rose from them as they saw its issue. They were now entirely cut off from all hope of succour, and their fate appeared to be sealed. Nevertheless they managed to send a message to the prince that they would hold out for three weeks longer in hopes that he might devise some plan for their relief, and carrier pigeons brought back word that another effort should be made to save them. But by this time the magazines were empty. Hitherto one pound of bread had been served out daily to each man and half a pound to each woman, and on this alone they had for many weeks subsisted; but the flour was now exhausted, and henceforth it was a battle with starvation.