The fortifications of Plymouth in Devon are extensive due to its natural harbour, its commanding position on the Western Approaches and its role as the United Kingdom's largest naval base. The first medieval defences were built to defend Sutton Harbour on the eastern side of Plymouth Sound at the mouth of the River Plym, but by the 18th century, naval activity had begun to shift westward to Devonport at the mouth of the River Tamar. During the Victorian era, advances in military technology led to a huge programme of fortification encompassing the whole of Plymouth Sound together with the overland approaches. Many of these works remained in military use well into the 20th century.
Medieval fortifications
At the time of the Norman Conquest, Plymouth was a tiny settlement at Sutton Harbour, but in 1295 and 1357, royal expeditions to France had used Plymouth as a final gathering place before making the crossing. In 1377, a murage grant was received to fund its fortification, although what form these works took is unknown.
Plymouth Castle
Following a French raid on Plymouth in August 1403, King Henry IV ordered the prior of Plympton and the abbot of Tavistock to further fortify the town with walls and towers. The eventual result of this was a castle with four towers overlooking the town and harbour, which seems to have been largely funded by the townspeople and was under the control of Plymouth's mayor and aldermen. Only a small section of the castle fabric survives, located in Lambhay Street, at the head of a flight of stairs leading down to the Mayflower Steps on the quayside.
The Barbican
Closely associated with the castle was a fortification right at the mouth of Sutton Harbour which gives its name to the present Barbican district. From depictions on Renaissance maps, it apparently consisted of a fortified jetty from which the harbour entrance could be "chained over when the need requireth".
Tudor fortifications
Tudor blockhouses
During the early Tudor period, six blockhouses were constructed at various points around Plymouth Sound. These were small artillery towers intended to command the stretch of water immediately in front of them. Fisher's Nose Blockhouse is sited on the headland at the eastern end of Plymouth Hoe and dominates the Cattewater, which is the approach to Sutton Harbour. It may have been built in the late 15th century and is shown on a chart dated 1540. It is currently in use as a café. Mount Edgcumbe Blockhouse is at the entrance to the Hamoaze, the estuary of the Tamar, at the western end of Plymouth Sound. Believed to have been built by the Edgcumbe family to protect their estates. It can still be visited. Devil's Point Blockhouse is on the headland opposite Mount Edgecumbe and the exterior can be viewed. Firestone Bay Blockhouse at Stonehouse may also have been built by the Edgcumbes. It is now a restaurant. Millbay West and Millbay East protected the harbour at Millbay but are no longer extant.
Elizabethan works
In 1590, Sir Francis Drake was appointed to improve the defences of Plymouth. After setting up some temporary artillery batteries on the Hoe and on St Anthony's Island, (later known as Drake's Island), he requested the funds to build a permanent fort on the Hoe and in 1592, Queen Elizabeth I imposed a local tax on pilchards for the purpose. Construction of the fort, later called Drake's Fort, continued until 1596 after Drake's death. The northern landward side of the fort was protected by two bastions and it enclosed the previously established batteries on the Hoe and also the Fisher's Nose Blockhouse. A further blockhouse called Queen Elizabeth's Tower was built a short distance to the west of Fisher's Nose. In July 1602 an Italian military engineer called "Frederick Genebelli" or Federigo Giambelli was appointed to supervise works at Plymouth fort.