For over two centuries there has been a military presence on Spike Island. In the 1770s, during the turmoil of the American War of Independence and at a time when Ireland was a key part of the British Empire, Cork and its harbour was used as an assembly and reception point for convoys.
There have been three forts on Spike Island. In 1789 building work began on a stone-built fort designed by Colonel Charles Vallancey to succeed an earlier earthwork fort, demolished in 1783 to save on rent costs. It was named ‘Fort Westmoreland’ in honour of John Fane, 10th Earl of Westmoreland and Lord Lieutenant of Ireland from 1789 to 1794.
The fort that exists today, the third fort, was constructed between 1804 and the 1860s and is a six-bastioned star-shaped fort. These artillery fortifications presented a low profile with sloping earthen sides to absorb cannon fire. The bastions were angled to maximize defensive fire from concealed positions within the fort and most of the buildings were well concealed to prevent bomb damage.
Over the course of its history, what is now called Fort Mitchel has been used as a base by the British and the Irish armies, the Irish Coastal Defence and the Irish Navy at various times.