The Medway was designated as a Class A harbour by the Home Ports Defence Committee, later the Home Defence Committee. The area included Chatham and Sheerness Dockyards one of the Royal Navies Most Important facilities. The Chatham Dockyard had its own array of defences, including land forts.
The primary defences for the Medway were:
- Grain Battery, Royal Commission recommendation, built between 1900 and 1901 with three 6-inch Mark VII guns
- Grain Fort a Royal Commission Fort built, between 1860 and 1867 and initially armed with sixteen guns facing the estuary. A Brenan Torpedo was later added. Between 1900 and 1901 two 9.2-inch Mark 10 guns were mounted to the top of the fort.
- Slough Fort was built between 1861 and 1869 with two wing batteries, each of two guns, being built between 1889 and 1891. In 1907 the right Wing Battery was remodeled to mount two 9.2-inch Mark X guns.
- Garrison Point Fort was a Royal Commission Fort and was built between 1862 and 1872 to two floor of casemated position for thirty six guns. By 1910 three 6-inch Mark VII guns and four 12-pdr Q.F. guns had been mounted on the roof of the casemates.
- Hoo Fort, Royal Commission Fort
- Darnet Fort, Royal Commission Fort