Lignery retreated to Fort Machault, from which he continued to direct harassing raids against the British in 1759. He was organizing an expedition against Fort Pitt (the fort built by the British on the site of Fort Duquesne) when he received an appeal for help from Pierre Pouchot, the commander at Fort Niagara. Pouchot had sent Lignery some troops, but was himself now under siege by the British and requested assistance. Lignery, who was trying to convince nearly 1,000 Indians to join in the attack on Fort Pitt at the time, convinced 500 to join his force of 800 troupes de la marine in a relief expedition. On June 24 his force was ambushed by the British as it neared Fort Niagara. The battle was a disaster for the French, and Lignery was seriously wounded and captured. Pouchot surrendered Niagara the next day, and Lignery died of his wounds on July 28.