The siege of Fort William Henry (3–9 August 1757, French: Bataille de Fort William Henry) was conducted by a French and Indian force led by Louis-Joseph de Montcalm against the British-held Fort William Henry. This fort, located at the southern end of Lake George, on the frontier between the British Province of New York and the French Province of Canada, was garrisoned by a poorly supported force of British regulars and provincial militia led by Lieutenant Colonel George Monro.
After several days of bombardment and increasing casualty rates, Monro surrendered to Montcalm, whose force included nearly 2,000 Indians from various tribes. The terms of surrender included the withdrawal of the garrison to Fort Edward, with specific terms that the French military protect the British from the Indians as they withdrew from the area.
In one of the most notorious incidents of the French and Indian War, Montcalm's Indian allies violated the agreed terms of surrender and attacked the departing British column, which had been deprived of ammunition, as it left the fort. They killed and scalped numerous soldiers and civilians, took as captives women, children, servants, and slaves, and slaughtered sick and wounded prisoners. Early accounts of the events called it a massacre and implied that as many as 1,500 people were killed, although it is unlikely more than 200 people (less than 10% of the British fighting strength) were actually killed in the massacre.Whether or not Montcalm and the other French officers present encouraged or opposed the actions of their Indians allies, and the total number of victims remains a matter of historical debate. The memory of the killings influenced the actions of British military commanders, especially those of General Jeffery Amherst, for the remainder of the war.