Fort Cumberland is a pentagonal artillery fortification erected to guard the entrance to Langstone Harbour, east of the Dockyard of Portsmouth on the south coast of England. It was sited to protect the Royal Navy Dockyard, by preventing enemy forces from landing in Langstone Harbour and attacking from the landward side. Fort Cumberland is widely recognised as the finest example of a bastion trace fort in England.The first fort (1747-1785)The first fort on the site was built by the Duke of Cumberland. Although there did previously exist an earthwork battery on the site, built in 1714. Work on Cumberland's fort commenced on January 1, 1747, and was substantially complete by the end of 1748. The fort had an irregular star shaped form, and was of earthwork construction. In section, the defences comprised a glacis, banquette and covered way, a dry ditch, berm, rampart, parapet and terre-plein. Within the body of the fort, a number of brick buildings were constructed, comprising a guardhouse, storeroom and powder magazine; of the two proposed barrack blocks, only one is believed to have been completed.