Portsmouth with its’ excellent harbour has been defended since Roman times. From 1495 with the building of the Round Tower, significant artillery fortification were built, including city walls and coastal defence batteries. Portsmouth Dockyard was built in 1496 and was the first Royal Navy Dockyard built.
In 1890 Portsmouth was designed as a A Class Harbour with Naval Dockyard and facilities. It had defences intended to resist attack from battleships. However, dating back to the times of Henry VIII, Portsmouth had been a key Royal Dockyard.