Towards evening a council was held, all the principal officers being present, and it was decided to evacuate the castle. It could indeed have been held for some days longer, but it was plain it would at length become untenable; the bridge of boats had already been struck in several places, and some of the barges composing it had sunk level with the water. Were it destroyed, the garrison of the castle would be completely cut off, and as no great advantage was to be gained by holding the position, for it was evident that it was upon the other end of the town the main attack was to be made, it was decided to evacuate it under cover of night. As soon as it became dark this decision was carried into effect, and for hours the troops worked steadily, transporting the guns, ammunition, and stores of all kinds across from the castle to the town. Already communication with their friends outside had almost ceased, for the first operation of the enemy had been to block the approach to Sluys from the sea. Boats had been moored head and stern right across Zwin, and a battery erected upon each shore to protect them; but Captains Hart and Allen twice swam down to communicate with friendly vessels below the obstacle, carrying despatches with them from the governor to the States-General, and from Roger Williams to the English commanders, urging that no time should be lost in assembling an army to march to the relief of the town. Both contained assurances that the garrison would defend the place to the last extremity, but pointed out that it was only a question of time, and that the town must fall unless relieved. The Dutch garrison were 800 strong, and had been joined by as many English. Parma had at first marched with but 6000 men against the city, but had very speedily drawn much larger bodies of men towards him, and had, as Roger Williams states in a letter to the queen sent from Sluys at an early period of the siege, four regiments of Walloons, four of Germans, one of Italians, one of Burgundians, fifty-two companies of Spaniards, twenty-four troops of horse, and forty-eight guns. This would give a total of at least 17,000 men, and further reinforcements afterwards arrived.