Bere Island is perhaps more widely known for its military heritage and is said to be one of the most fortified locations in Ireland, featuring two Martello towers, a signal tower, the remains of seven gun batteries and assorted fortifications from the British Admiralty base that was located on the island during the early 1900s.
The start of a military interest in Bere Island began in 1602, when Sir George Carew and his forces landed at Lonehort Harbour, and ordered a road to be built across the island to transport his army to the western end of the island, which directly overlooked Dunboy Castle, the stronghold of the Gaelic chieftain, Donal Cam O’Sullivan Beare. The Siege of Dunboy started on 5th June 1602. Over 5,000 soldiers under the command of Sir George Carew besieged the castle, eventually capturing it after 11 days.
In December 1796, a French fleet led by General Hoche and under the direction of General Theobald Wolfe Tone entered Bantry Bay. Adverse winds prevented the main force from landing, however a longboat did manage to land on the eastern shore Bere Island. Its crew were captured, and the longboat (the oldest surviving vessel of the French Navy) is now in the National Museum of Ireland.
In August 1798, there was a further invasion attempt, at Killala in Co Mayo following the Irish Rebellion that year. As a result of these events the British authorities drew up a plan of defence for Ireland, which included improving security at Bantry Bay. Rear Admiral Sir Robert Calder who commanded the naval squadron based in Castletownbere requested protection for his supply ships which were based in the Berehaven anchorage off Bere Island. William Cathcart, the 1st Earl Cathcart ordered his engineers to build four Martello Towers on Bere Island. These were completed in 1805 (two of which remain to this day) along with a signal tower barracks, a quay and associated storage buildings.
Following the end of the Napoleonic Wars there followed a period of military stagnation. This ended in 1898 when the British Military raised a compulsory order on 17th March 1898 for the east end of the island. Additional fortifications were constructed, including seven gun batteries, the largest of which was Lonehort Battery. The battery constructed at Lonehort was the most strategic and consisted of two 6″ guns and one 9″ gun.
The primary role of these fortifications was to provide protection to British Dreadnoughts when they were in port, The ships needed 48 hours of protection while routine maintenance was undertaken and until they got up sufficient steam in their boilers.
Berehaven remained in the hands of the British during the First World War and was also used by the American Navy in WW1. Division 6, of the US Navy, which was composed of the Utah (flagship), Nevada, and Oklahoma, were based at Berehaven, its principal duty being to protect Atlantic convoys from possible enemy raiders.
During the War of Independence an Internment camp was in operation on Bere Island, the camp closed on December 10th 1921. In 1922, under the terms of the Anglo-Irish Treaty the British withdrew from most of Ireland apart from three deep water ports, at Berehaven, Queenstown (now Cobh) and Lough Swilly, which became known as the Treaty Ports. These remained in British control until 1938. On September 26th 1938 Fort Berehaven, Bere Island was handed back to the Irish Government. The barracks and firing range on Bere Island are still used for training purposes by the Irish Defence Forces.