chain across the River Medway for extra defence in 1585. Hawkins' chain was later replaced with a boom of masts, iron, cordage, and the hulls of two old ships, besides a couple of ruined pinnacles. The Lines With the failure of Upnor Castle, it was seen necessary to increase the defences. In the event, those defences were built in distinct phases, as the government saw the increasing threat of invasion: 1669 Fort Gillingham and Cockham Wood Fort built. 1756 Chatham Lines built, to designs by Captain John Desmaretz (who also designed the Portsmouth fortifications). This fortification, and its subsequent upgrading, were to concentrate on an overland attack and so were built to face south. They included redoubts at Amherst and Townsend. The Lines enclosed the entire dockyard on its eastern side. 1778–1783 Further improvements were carried out, to the designs of Captain Hugh Debbeig at the bequest of General Amherst. In 1782, an Act of Parliament increased the land needed for the Field of Fire. 1805–1812 Amherst redoubt, now Fort Amherst; new forts, named Pitt and Clarence. The Lines were also extended to the east of Saint Mary's Creek (on St Mary's Island). 1860s Grain Fort, and other smaller batteries in that area. 1870–1892 A number of forts built at a greater distance from the dockyard: Forts Bridgewood, Luton, Borstal, Horsted and Darland. These became known as the "Great Lines". Forts Darnet and Hoo built on islands in the River Medway. Associated barracks The Dockyard led to large numbers of military personnel being garrisoned in Chatham and the surrounding area. A good many were engaged in manning the defences, but some had other duties; others were accommodated there for convenience prior to embarking on ships for duties overseas, or following their disembarkation. Initially, soldiers were housed under canvas or else billetted in houses and inns, but from the 18th century barracks began to be constructed. The oldest surviving barracks in the Chatham area is in Upnor; dating from 1718, it housed the detachment of 64 men responsible for guarding the gunpowder store in Upnor Castle. Infantry Barracks (Kitchener Barracks) Chatham Infantry Barracks was opened in 1757 to house troops manning the fortifications which had recently been built to defend the Dockyard. Accommodating some 1,800 men, Chatham was one of the first large-scale Army barracks in England. Built on sloping ground east of the Dockyard, the rectangular site (enclosed within its