The operation was successful. The Spaniards, finding their line of communication threatened, advanced in force from their position by the sea, and their forts opened a heavy fire on the little work thrown up. Other similar attempts would have been made to harass the Spaniards and divert them from their main work, had not Sir Francis Vere been severely wounded in the head on the 4th of August by a shot from the Spanish batteries, which continued to keep up a tremendous fire upon the town. So serious was the wound that the surgeons were of opinion that the only chance of saving his life was to send him away from the din and turmoil of the siege; and on the 10th he was taken to Middelburg, where he remained for a month, returning to Ostend long before his wound was properly healed.

On the 1st of August a batch of recruits had arrived from England, and on the 8th 1200 more were landed. The fire of the besiegers was now so heavy that the soldiers were forced to dig underground quarters to shelter themselves. Sir Horace Vere led out several sorties; but the besiegers, no longer distracted by the feints contrived by Sir Francis, succeeded in erecting a battery on the margin of the Old Haven, and opened fire on the Sand-hill Fort.

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 south-east 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.

They were unanimously of opinion that the force was too small to defend the whole, but Sir Horace Vere and Sir John Ogle alone gave their advice to abandon the outlying forts rather than endanger the loss of the town. The other officers were of opinion that all the works should be held, although they acknowledged that the disposable force was incapable of doing so. Some days elapsed, and Vere learned that the Spanish preparations were all complete, and that they were only waiting for a low tide to attack. Time was everything, for a change of wind would bring speedy succour, so without taking council with anyone he sent Sir John Ogle with a drummer to the side of the Old Haven.

Don Mateo Serrano came forward, and Ogle gave his message, which was that General Vere wished to have some qualified person to speak to him. This was reported to the archduke, who agreed that Serrano and another Spanish officer should go into the town, and that Ogle and a comrade should come as hostages into the Spanish camp. Sir John Ogle took his friend Sir Charles Fairfax with him, and Serrano and Colonel Antonio crossed into Ostend. The two Englishmen were conducted to the archduke, who asked Sir John Ogle to tell him if there was any deceit in the matter. Ogle answered if there were it was more than he knew, for Vere had simply charged him to carry the message, and that he and Fairfax had merely come as hostages for the safe return of the Spanish officers.

Ogle was next asked whether he thought the general intended sincerely or not, and could only reply that he was altogether unacquainted with the general's purpose.

The next morning Serrano and Antonio returned without having seen Vere. The pretext on which they had been sent back was that there was some irregularity in their coming across; but instead of their being sent back across the Old Haven they were sent across the Geule, and had to make a long round to regain the archduke's camp.