1798 rebellion, was intercepted and defeated in a naval battle at the entrance to Lough Swilly. Subsequently Tone was captured and taken ashore at Buncrana on the east side of the Swilly. A subsequent reassessment of the threat of invasion led to the building of a series of fortifications guarding the different approaches and landing points within the lough which were completed between 1800 and 1820. Martello towers were built around 1804 to defend the approaches to Derry. The six on the lough cost €1,800 each, were armed with smoothbore cannon, firing round shot and were completed in six months. Immediately prior to the First World War the War Office improved the Napoleonic forts and their armaments as well as adding another fort at the entrance to the lough at Lenan Head with guns (12-mile range) – the largest in Ireland at the time. The remains of these fortifications are still at Lenan Head Fort, Fort Dunree (now a military and wildlife museum), Ned's Point, Buncrana, Inch Fort and on the west coast at Rathmullan, Knockalla and Macamish Point. During the First World War, the lough was used by the Royal Navy as an anchorage for elements of the Grand Fleet, an amalgamation of the pre-war Home and Atlantic Fleets, under Admiral Sir John R. Jellicoe and a gathering/staging point for Atlantic convoys. During this period a boom was placed across the lough between Macamish Point and Ned's Point, supported by a number of trawlers, to prevent U-boat attacks. After the Irish War of Independence the lough was also one of the Treaty Ports specified in the Anglo-Irish Treaty until its final handing over at Fort Dunree in 1938. According to exhibits at Fort Dunree, during World War II Irish troops operated the guns there with explicit instructions to fire at any ship that might threaten Irish neutrality by entering the natural harbour. There was reportedly only one serious incident, when a Royal Navy ship entered the lough and did not initially respond to signals that it should turn back. However, the ship turned around before Irish forces fired upon it. References Notes Sources See also List of loughs in Ireland Londonderry and Lough Swilly Railway Buncrana Geography of Letterkenny Sea loughs of the Republic of Ireland Fjords of the Republic of Ireland Landforms of County Donegal