Which British fort on Lake Ontario was captured by the French in 1756?

Fort Oswego was the British fort on Lake Ontario captured by the French in 1756. The victory came during the early North American fighting of the Seven Years’ War, known in the colonies as the French and Indian War.

French commander Louis-Joseph de Montcalm led roughly 3,000 French regulars, Canadian militia, and Indigenous allies against the British fortifications at Oswego in August 1756. The position was actually a complex of defenses, including Fort Oswego, Fort Ontario, and Fort George. Montcalm first seized Fort Ontario, gaining a commanding position across the river.

British commander Colonel James Mercer was killed by a French shell during the bombardment. The garrison then surrendered, giving the French about 1,700 prisoners as well as artillery, boats, and supplies. The French destroyed the fortifications after the victory rather than maintaining them as a permanent base.

Fort Ontario is the most likely source of confusion because it was part of the same defensive complex and was captured first. However, the British fort specifically identified in the question as the main 1756 capture was Fort Oswego, also known to the French as Fort Chouaguen.