Archaeological evidence suggests that an Iron Age fort was built on the hilltop around 500 to 600 BC and that the castle itself was built around 1370-1400. In 1616 the gateway and walls had to be repaired at the expense of the five northern parishes. A powder house, guardroom and houses for the garrison were added around this time. During the English Civil War Parliamentarian troops may have been stationed in the Castle. Extensive repairs were recommended in 1680 after the Civil War but it was abandoned shortly after. Nearly a century later it was reported to be in a state of disrepair. The increased threat of invasion during the American War of Independence from 1778-1783 prompted the castle's complete repair and the building of barracks and garrison by regular army troops. Two divisions of Russian troops were stationed in Guernsey, Alderney and Jersey in 1799. Hundreds of them contracted disease and the dead were buried close to the Vale Castle. By the end of C19 the barracks were abandoned, not for the first time, and fell into a neglected state. During World War I the local militia had a small garrison in the castle and between the wars the barracks were used by the States as homes. German forces demolished the barracks during the Occupation from 1940-1945 and built concrete fortifications in and around the castle. Thus the site has been used for military purposes for over two thousand years.