Pendennis Castle is one of a number of circular coastal artillery forts built along the south coast of England by Henry VIII to defend important harbours and ports in the event of invasion by France and Spain. Together with St Mawes on the opposite shoreline, Pendennis guarded against the capture of the strategic anchorage at Carrick Roads and the port of Falmouth.

The 16th century fortification also played a role during World War 2 as the Command Centre for Cornwall, protecting the western approaches to Britain.