Plymouth initially had defences concentrated around the dockyard area, including the Citadel and blockhouses.
Plymouth was subsequently designated as a Class A Port by the Home Ports Defence Committee, later the Home Defence Committee with a main Naval Base and Dockyard. Defences of the port were designed to resist attack by Battleships.
The first phase of new fortifications after the Napoleonic Wars were built between 1847 and 1849 and included:
Picklecombe and Staddon Point were limestone casemated batteries mounting heavy guns. They were later redeveloped.
The 1860 Royal Commission recommended some 30 sites be developed and these were largely built between 1860 and 1872. The coastal defence fortifications outlined in the 1860 report were from west to east:
The land defences for Plymouth from west to east were:
While the Royal Commission Forts of 1860 had been continually amended, the introduction of Rifled Muzzle Loading (RML) guns from 1870 onwards led to many changes. Between 1880 and 1900, when breech loading guns were fully introduced, the following additional fortifications were built:
The final phase of development was the introduction of Breech Loading (BL) guns of 9.2-inch, 6-inch and 12-pdr calibre between 1900 and 1914. Some were mounted in old RML Batteries. These were:
Plymouth Submarine Mining Establishment was built on a narrow strip of land between the Citadel and the harbour. Construction commenced in 1884 and the works were completed on 31st March 1888.