thumb|right|300px|The walls of Portsmouth and the [[HMNB Portsmouth|dockyard in 1773. The dockyard is to the north of the town and separated from it by the mill pond. To the East of the town is the Little Morass, an area of marshland.]]

The fortifications of Portsmouth are extensive due to its strategic position on the English Channel and role as home to the Royal Navy. For this reason, Portsmouth was, by the 19th century, one of the most fortified cities in the world.

During the 14th century, Portsmouth was subject to attacks in 1338, 1369, 1377 and 1380. Evidence suggests that simple earthworks were constructed and reconstructed around the settlement in response. The first structure built to defend Portsmouth proper was a wooden version of the Round Tower constructed between 1418 and 1426.

Expansion under the Tudors

thumb|right|A map of Portsmouth showing the defences in the time of Henry VIII.

During Henry VII's rule, the Round Tower was rebuilt in stone and the Square Tower added. It appears likely that what is now known as the "saluting platform" was also built during Henry VII's reign. Southsea Castle at the southern tip of Portsea Island was built by his son and successor Henry VIII.

To the north of the city, it is believed that a small fortification was constructed to defend the bridge across Portsbridge Creek. In 1522, the first of several defensive chains that could be raised in an attempt to block the harbour entrance was ordered.

By 1542, Portsmouth was surrounded by defensive ramparts and towers built from earth and wood. One tower was positioned on the corner where the wall extending from the saluting platform met the wall running along the southeast rampart of the town. The southeast rampart was also equipped with what appears to be a firing platform, while another tower was constructed on the corner where the ramparts to the south east and the northeast of the town met. In the centre of the northwest rampart was the town gate defended by a structure known as The Mount which also acted as a bastion. Finally, the wall to the north of the town had a tower at each end one where it joined the northeast wall and one where it met the sea. A wooden wall was constructed between the Round Tower and the saluting platform at around the same time.

The next phase of expansion started in the late 1550s and continued through the rest of Elizabeth I's reign. The ramparts were updated and the gabions along the edge of the Camber and the palisade that cut off Portsmouth point were replaced by stone wall. Other works including improving the various towers with some of them developing into bastions. Sometime around 1600 a new gate known as point gate replaced the North Gate in controlling access to Portsmouth point.

During the Civil War

At the time of the Civil War, the fortifications mounted around 100 guns and when properly manned were considered by some to be able to withstand a siege of 40,000 men. In one of the first actions of the civil war Parliament managed to capture the city from the royalist forces during the Siege of Portsmouth.

Reconstruction under Charles II

280px|thumb|right|Map, c.1668, showing Portsmouth's fortifications, together with [[Fort Blockhouse on Gosport point and a defensive chain across the harbour entrance.]]

In 1665, Charles II ordered Bernard de Gomme to begin the reconstruction of Portsmouth's fortifications, a process which was to take many years. The year before this a new chain to block the harbour entrance was ordered at a cost of £200. Later in the 1680s Southsea castle was rebuilt.

thumbnail|left|Round Tower and Point Battery

On the shoreline a new battery was built at the end of Portsmouth point facing Gosport.

While the towns defences were being strengthened some thought appears to have been given to their aesthetic appearance.

thumb|280px|right|Copy of de Gomme's plan of 'Portsmouth, the Docke, Gosport town and Gosport pointe' in 1668.

In 1679 Sir Bernard de Gomme built barracks within the town to accommodate two Companies of Foot (120 men) to man the defences. His plan and specification for the building (a double range of ten bays, long by deep) represents 'the earliest known detailed drawing of a barracks in England'. The soldiers slept two to a bed, four to a room, with additional rooms being provided for officers at each end of the block, and for sergeants in the middle of the ground floor. By 1684 there were barracks in addition at the Round Tower, and a two-storey block at the Landport Gate.

The first true fortification of the dockyard was constructed between 1665 and 1668 although there had previously been a wall around it.

Later in the 17th century in 1688 the fort protecting the crossing across Portsbridge creek was rebuilt under the direction of the Chief Royal Engineer Sir Martin Beckman.

The sheer manpower required by de Gomme's defences meant that after about 1730 the double moat system used around Portsmouth was abandoned with the outer moat being filled in.

At the same time the defences started to focus on protecting the whole of Portsea island. The first Fort Cumberland was constructed to prevent hostile forces from sailing to Langstone harbour and the first Lumps Fort and Eastney battery were built to protect Eastney beach.

Fort Cumberland and Lumps Fort were significantly rebuilt.

The Portsea fortifications were expanded slightly in the 1840s and 1860s as the dockyard was extended.

The city walls though were for the most part removed in the 1870s and 80s a task accomplished through the use of convict labour.

20th century

Improvements in artillery technology had rendered the various landward facing fortifications obsolete over the turn of the century and by the end of the first decade they largely disarmed.

During WW2 anti tank defence blocks were constructed on Fraser Beach. Pill boxes were constructed to defend Portsmouth Airport in the form of Pickett-Hamilton Forts. A new concrete gun emplacement which contained a single 75mm gun was constructed on the eastern part of the Hilsea lines.

The remaining defences were deactivated when the UK abandoned coastal artillery in 1956.

thumb|right|The pair of links from one of the [[boom (navigational barrier)|harbour boom chains that is on display at Southsea Castle]]

Antitank defence blocks on Fraser Beach are now a Grade II listed structure. One of the Pickett-Hamilton forts constructed to protect the airport was on display outside the D-Day Story in Southsea. This was removed in 2017 when the museum was refurbished.

See also

  • List of fortifications
  • King James's and Landport Gates

References

  • The Square Tower, Old Portsmouth
  • FOOPA Old Portsmouth Fortifications
  • Palmerston Forts Society