Georges Island was fortified from about 1750 by the British. Initially there was a battery contained seven 32-pdr SB guns behind earthen ramparts. The facing of the battery was Southwest to cover the entrance to the main anchorage from the open sea. In 1755 an further nine 24-pdr SB gun were added to the armament, with barracks, an underground magazine and crew shelters following.
By 1783 the coastal defence battery had a total of forty eight guns including six 42-pdr SB guns, twenty-nine 24-pdr SB guns, three 18-pdr SB gun, nine 12-pdr SB gun and a single 6-pdr SB. Various earthworks were added to protect the battery from enemy fire and infantry attack.
Within a decade the fortifications were improved with the building of Fort Charlotte, see separate entry. This star fort was completed in 1798 and a Martello Tower added by 1813.
The other major defence facility on the Island was the Submarine Mining Established. The first building were constructed between 1873 and 1877 and then expanded between 1885 ns 1893.