In 1779, Brant visited Montreal, where some of her children attended school. She returned to Fort Niagara when the Americans began their Sullivan Expedition that year. In retaliation for attacks in Cherry Valley, the expedition attacked 40 Seneca and other Iroquois villages throughout central western New York, destroying crops and winter stores. Because of the war, Brant could get only as far as the British post at Carleton Island, where many Iroquois refugees had fled from the Americans. There she continued her work as an intermediary. The British commander considered Brant's influence "far superior to that of all their Chiefs put together". Brant was unhappy with having to live in an army barracks with her children. Hoping to keep her favor, the British built her a house on the island in 1781, where she lived with her children and four slaves for the remainder of the war. Throughout the war, Brant played important roles as a negotiator, mediator, liaison, and advocate for Mohawk and Iroquois peoples at Fort Niagara, Montreal, and Carleton Island.