In 1665 a Dutch fleet sailed up the River Medway and invaded Gillingham before being driven out. During the Napoleonic Wars, lines of gun emplacements were set up facing the Medway on an escarpment between Gillingham and Chatham which is still known as the Great Lines.
In 1919, following World War I, a Naval War Memorial in the shape of a white stone obelisk was set up on the Great Lines, from where it can be seen for many miles; additional structures were added in 1945 to commemorate the dead of World War II. Identical monuments stand in the Dockyard towns of Portsmouth and Plymouth.
The traditional industry of the area was maritime, with employment at Chatham Dockyard, most of which actually lay within Gillingham. This is largely diminished; the Dockyard ceased to be a Naval base in 1984. Gillingham is firmly within the commuter belt for London.