All conquering powers need to guard against not only internal rebellion but also attack from an external force. So it was that over several centuries the British authorities remained on the alert for the possibility of Ireland being invaded by a rival power.  This being an island, the invaders would initially be seaborne but their means of assault changed as methods of warfare became more sophisticated and potentially more lethal. Once ocean-going ships capable of carrying cannon were developed, coastal defences had to adapt as earlier methods of resistance threatened to be ineffective. Hence the construction of Charles Fort outside Kinsale, County Cork.

Located at the mouth of the river Bandon, Kinsale harbour is virtually landlocked, providing good shelter and anchorage to sea vessels. When Philip III of Spain sent an expeditionary force here in 1601 to support the indigenous army then fighting the English crown, it disembarked at Kinsale. So too did James II, accompanied by a contingent of French troops, in 1689. Understandably Kinsale was seen by the governing authorities as a vulnerable point of entry, and therefore in need of defence. Already in the immediate aftermath of the Battle of Kinsale, the pentagonal James Fort had been erected to the south of the port, but well before the end of the century this was judged insufficient. The development of another and bigger fortification began on the opposite side of the harbour. This is Charles Fort, named after Charles II.

There seems to be a degree of uncertainty over who was responsible for the design of Charles Fort. Stylistically it derives from the system of fortifications developed by the Marquis de Vauban (1633-1707), a French soldier and military engineer who among much other work in the course of a busy life oversaw the building of some thirty-seven new fortresses and fortified harbours in his native country. Vauban’s star-shaped fortifications featuring a sequence of acute angles allowed defendants of a building better to see and repulse any assault, as well as to withstand cannon fire. This design was much emulated from the second half of the 17^th century onward and accordingly served as inspiration for Charles Fort. Built between 1678 and 1683, the fort was planned as a pentagonal star but the completed structure is simpler and lacks adequate landward bastions (it can also be overlooked from higher ground, which proved a serious drawback during the Williamite Wars). Nevertheless it is one of the largest and most impressive fortifications ever erected here, with massive seaward bastions and ramparts featuring gun platforms and embrasures, glacis (a bank sloping down from the building which leaves potential attackers exposed) and a citadel. The interior of the fort runs to some twenty acres, much of which is filled with the remains of military accommodation.

Sir William Robinson, then Surveyor-General in Ireland, is said to have played a role in the development of Charles Fort, but so too it seems did Roger Boyle, Earl of Orrery – a polymath who was both soldier and playwright, gentleman-architect and engineer – and James Archer, a Roman Catholic architect and engineer who managed to survive several changes of regime. Internally, the majority of the buildings are later than the fortifications. The limestone pedimented gateway, for example, was put in place in 1759 (incorporating older fabric) and may have been designed by Thomas Roberts who was then employed in erecting new buildings inside the fort. One of the houses on site, first occupied by Governor Walander, dates from 1710 and also features a neo-classical pedimented doorcase. Other blocks are from different periods in the 18^th century. The passage of time and a long period of neglect in the last century mean that today it is difficult to tell what dates from when. Charles Fort remained in use by the British armed forces until their departure in the aftermath of the Anglo-Irish Treaty in December 1921. The following year the site was set alight by anti-treaty forces and badly damaged. Charles Fort thereafter fell into ruin until the early 1970s when it was declared a national monument and partially restored: in this condition it has been open to the public ever since.…