Ft. Henry had been under siege for nearly a month, and just days ago the French succeeded in the siege, forcing Col. Munro to surrender to the French General Montcalm under these conditions: 1. The British militia at Ft. Henry be dismantled; 2. The frontier farmers serving in the militia return peacefully to their lands; 3. The British turn over control of Fort William Henry to the French; 4. The British military at Ft. Henry return to England. If these conditions were met, the French would take over the fort without incident.
Midway into the siege, Col. Munro had sent messengers to General Webb, the man in charge of the British military presence in the region, telling Webb of the desperate need of reinforcements at Ft. Henry. It became apparent that the French or their Indian allies must have intercepted the messengers, for the men and supplies never arrived.
The French had themselves entrenched around the fort, gradually working their way closer. When they got within 200 yards of the fort, they began that night their mortar fire. In the morning, General Montcalm pleaded Munro to surrender so as to end the senseless waste of human life. He gave Munro the conditions of surrender, and Munro accepted them.
While defending the fort, many of the militia wanted to return to their farms and defend them against the raids of the Indians allied with the French. Munro denied them that request. Later Nathaniel helped them to get safely out of the fort. He was locked up for this act.
We now know that the French had no intentions of keeping to the terms of the surrender. Shortly after daybreak, the colonel led everyone out of the fort and they began to mark to Albany. However, only a few miles into the march, Magua and his Hurons ambushed the group.
It is unclear who other than Col. Munro died in the attack. The savages fought mercilessly, killing whomever they saw, be it man, woman or child. One survivor of the massacre who barely himself escaped alive, though not uninjured, says Magua himself killed Munro, and in an act of pure carnage, cut out the colonel's heart.
In the fight with the Hurons, Nathaniel escaped his chains and is now at large. The charges against him have been dropped due to the valor with which he fought in the ambush.