Great Britain France The Battle of the Thousand Islands was an engagement fought on 16–24 August 1760, in the upper St. Lawrence River, among the Thousand Islands, along the present day Canada–United States border, by British and French forces during the closing phases of the Seven Years' War, as it is called in Canada and Europe, or the French and Indian War as it is referred to in the United States.

The engagement took place at Fort Lévis (about one mile (1.6 km) downstream from the modern Ogdensburg–Prescott International Bridge), Pointe au Baril (present-day Maitland, Ontario), and the surrounding waters and islands during the Montreal Campaign.

By August 1760, the French were building Fort Lévis at Île Royale (present-day Chimney Island New York) in the St. Lawrence River.

l'Iroquoise, under command of Commodore René Hypolite Pépin dit La Force, was armed with ten 12-pound cannon and swivel guns .

After the fall of Quebec in the 1759 Battle of the Plains of Abraham, British Commander-in-Chief General Jeffery Amherst prepared to launch a three-pronged attack to take Montreal.

Captain Joshua Loring, who commanded the British snows Onondaga and Mohawk, had been sent ahead of Amherst's force as an advance guard.

On 7 August, French lookouts sighted Onondaga and Mohawk from their outpost at Ile aux Chevreuils, upstream from Fort Lévis.

Fearing the remaining French ship might attack his transports, Amherst ordered Colonel George Williamson to capture l'Outaouaise the following day.

The captured l'Outaouaise was repaired and renamed Williamson, to be put back into service by Captain Patrick Sinclair against her former owners.

Williamson was hit 48 times by the five French guns when it joined in with the British batteries firing on Fort Lévis from surrounding islands.

The three-pronged British forces totaling 17,000 men began to converge on the town, burning villages along the way and prompting mass desertions from the Canadian militia.