The besiegers secretly massed a large force in the trenches.

At midday on the 22d a salvo of four mortars gave the signal.

The French rushed in with loud shouts and effected a complete surprise.

Before the troops could get under arms two bastions were captured.
So sudden was the affair that many of the English officers, hearing the firing, ran out from the keep, and seeing some foreign troops drawn up in the works joined them, concluding that they were Dutch, and were only undeceived by finding themselves taken prisoners.

The men were so confused by the loss of many of the officers that, had the French pushed in at once, they would have been able to carry the main body of the works with but little resistance.