The only advantage it gave them, would have been that it would have enabled them to attack the lower gate of the fort, protected by its outer wall from the fire of the hill battery.
Charlie had, however, perceived that this would be the case, and had planted a number of mines under the wall at this point.

These were exploded when the defenders of the town entered the fort, and a hundred yards of the wall were thus destroyed; leaving the space, across which the enemy must advance to the attack of the gate, exposed to the fire of the hill battery, as well as of the numerous guns of the fort bearing upon it.
Two days passed without any further operations on the part of the enemy; and then Bussy, seeing that nothing whatever could be done towards assaulting the fortress, so long as the battery remained in the hands of the besieged, determined to make a desperate effort to carry it, ignorant of its immense strength.

At night, therefore, he ordered two bodies of men, each fifteen hundred strong, to mount the hillside, far to the right and left of the town; to move along at the foot of the wall of rock, and to carry the battery by storm at daybreak.
Charlie, believing that such an attempt would be made, had upon the day following the fall of the town taken his post there, and had ordered a most vigilant watch to be kept up, each night; placing sentries some hundred yards away, on either side, to give warning of the approach of an enemy.
Towards daybreak on the third morning a shot upon the left, followed a few seconds later by one on the right, told that the enemy were approaching.

A minute or two afterwards the sentries ran in, climbed from the ditch by ladders which had been placed there for the purpose, and, hauling these up after them, were soon in the battery, with the news that large bodies of the enemy were approaching on either flank.
Scarcely were the garrison at their posts, when the French were seen approaching.

At once they broke into a run, and, gallantly led, dashed across the space of cleared rock, in spite of the heavy fire of musketry and grape.
When they came, however, to the edge of the deep gulf in the solid rock, they paused.