In July 1759, the French began a campaign to retake Fort Pitt. Nearly a thousand French and Canadiens and a thousand Native Americans mustered at Fort Machault. The British, however, began a siege of the French Fort Niagara. On July 25, 1759, the French surrendered Fort Niagara. This made the French garrisons in the Ohio Country untenable. They abandoned their assault on Fort Pitt and available forces were sent to attempt to relieve Fort Niagara.