On 23 June 1713, the French residents of Nova Scotia were given one year to declare allegiance to Britain or leave the region. In the meantime, the French signalled their preparedness for future hostilities by beginning the construction of Fortress Louisbourg on Île Royale, now Cape Breton Island. The British grew increasingly alarmed by the prospect of disloyalty in wartime of the Acadians now under their rule. French missionaries worked to maintain the loyalty of Acadians, and to maintain a hold on the mainland part of Acadia.