On the 19th of September Sir Francis Vere returned to the town, to the great joy of the garrison. Reinforcements continued to arrive, and at this time the garrison numbered 4480. There were, too, a large number of noblemen and gentlemen from England, France, and Holland, who had come to learn the art of war under the man who was regarded as the greatest general of the time. All who were willing to work and learn were heartily welcomed; those who were unwilling to do so were soon made to feel that a besieged city was no place for them. While the fighting was going on the archduke had attempted to capture the place by treason. He engaged a traitor named Coningsby; who crossed to England, obtained letters of introduction to Vere, and then went to Ostend. Thence he sent intelligence to the besiegers of all that took place in the town, placing his letters at night in an old boat sunk in the mud on the bank of the Old Haven, a Spaniard wading across at low tide and fetching them away. He then attempted to bribe a sergeant to blow up the powder magazine. The sergeant revealed the plot. Coningsby was seized and confessed everything, and by an act of extraordinary clemency was only sentenced to be whipped out of town. This act of treachery on the part of the archduke justified the otherwise dishonourable stratagem afterwards played by Vere upon him. All through October and November the Spaniards were hard at work advancing their batteries, sinking great baskets filled with sand in the Old Haven to facilitate the passage of the troops, and building floating batteries in the Geule. On the night of the 4th of December they advanced suddenly to the attack. Vere and his officers leapt from their beds and rushed to the walls, and after a fierce struggle the besiegers were driven back. Straw was lighted to enable the musketeers and gunners to fire upon them as they retreated, and the assault cost them five hundred lives. On the 12th a hard frost set in, and until Christmas a strong gale from the southeast blew. No succour could reach the town. The garrison were dwindling fast, and ammunition falling short. It required fully 4000 men to guard the walls and forts, while but 2500 remained capable of bearing arms. It was known that the archduke soon intended to make an assault with his whole force, and Vere knew that he could scarcely hope to repel it. He called a council of his chief officers, and asked their opinion whether with the present numbers all parts of the works could be manned in case of assault, and if not whether it was advisable to withdraw the guards from all the outlying positions and to hold only the town.