After the Treaty of Utrecht of 1713 which transferred Acadie to Great Britain, the French decided to build the fortress town of Louisbourg on île Royale (today's Cape Breton). Because of its strategic position it became known as the « Gibraltar of America ». Conquered by Great Britain in 1745, Louisbourg was returned to France in 1748 after the Treaty of Aix-la-Chapelle. As France had been trying to reclaim Acadie since 1744, in 1749, in order to counterbalance the fortress of Louisbourg and strengthen their demographic and military, in the area, the British founded a new capital, Halifax. After the arrival of many new British troops in Nova Scotia, and seeing their land becoming more and more British, hundreds of Acadians left and settled in île Saint-Jean (today's Prince Edward Island) or in Chignetou (on the border of between modern-day Nova Scotia and New Brunswick) where France had built Forts Beauséjour and Gaspareaux.