Treaty Ports (Ireland)
Following the establishment of the Irish Free State, three deep water Treaty Ports (Irish: Calafoirt an Chonartha) at Berehaven, Spike Island (off modern Cóbh), and Lough Swilly were retained by the United Kingdom in accordance with the Anglo-Irish Treaty of 6 December 1921. The main reason for the retention of the ports was the U-boat Campaign around Irish coasts during World War I and the concern of the British government that it might recur.