The 1710 conquest of the Acadian capital of Port Royal during the war was confirmed by the Treaty of Utrecht of 1713. The British conceded to the French "the island called Cape Breton, as also all others, both in the mouth of the river of St. Lawrence, and in the gulph of the same name", and "all manner of liberty to fortify any place or places there." The French established a fortress at Louisbourg, Cape Breton, to guard the sea approaches to Quebec.