On the morning of the eighth of August the cannon firing ceased, just as the last express from Colonel Monroe arrived stating that he must give up the fort unless at once relieved.
The ammunition of the beleaguered garrison was almost exhausted, many of their cannon were split, some of the soldiers were sick with smallpox, and their losses in killed and wounded amounted to more than three hundred men.

The end was inevitable, and it came after General Webb had sent a letter to Colonel Monroe advising him to surrender.

This letter was intercepted by Montcalm, who thus knew the exact situation and acted accordingly.

He sent the letter to Colonel Monroe, with an urgent demand for surrender, promising him most liberal terms, and the despairing officer, who had gallantly defended the fort to the last, gave in and threw himself upon the mercy of his foe.
The Marquis de Montcalm may have intended to keep his stipulations, which were that the garrison should be protected by an escort of French troops to Fort Edward, and their sick and wounded cared for.

Relying upon these terms, they marched out of the fort without arms or baggage, but were no sooner clear of the gates than they were set upon by more than two thousand Indians, excited by the liquor they had discovered and drunk, and frenzied at the prospect of the escape of their foes.