Chatham Dockyard dates back to the middle of the 16th Century and expanded over the years into Gillingham. The Royal Navy Dockyard at Chatham was a major site for building warships and at its’ height employed over 10,000 skilled workers. The site had limitations because of the tidal flow, and Sheerness was developed as an alternate victualling location for a quicker turn around. Sheerness remained active until 1959 as a subsidiary to Chatham Dockyard.
The Chatham Dockyard had always been protected by fortifications, but the Dutch attack of 1667, when they captured Sheerness and used it as a base of operations to attack the Royal Navy in the Medway, led to major improvements.
Chatham was slowly superseded by Portsmouth and Plymouth in the 19th Century.
1667 Cockham Wood Battery and Gillingham Battery built to defend the dockyard.
Construction of the Great Lines of Chatham began in 1756. This was a line of bastion fortifications about two miles long, protecting Chatham Dockyard from land attack. There were redoubts at each end of the Lines, Towsend Redoubt in the North and Amherst Redoubt in the South.
During the Napoleonic Wars (1805-12) the defences of Chatham were expanded. The Amherst Redoubt was reinforced and developed into Fort Amherst with a complex of tunnels, dry moats and gun batteries.
Also built at this time were Fort Pitt (1805-19) , a pentagonal bastioned fort and Fort Clarence (1805-11), a gun tower.