[1] The site consists of the original battery and barracks, designed by Colonial Architect James Barnet, located at the end of Suakin Drive, Georges Heights, two later batteries located adjacent to the corner of Middle Head Road and Best Avenue, Georges Heights, and the Beehive (or Lower) Casemate adjacent to the Armoured (or Upper) Casemate in Chowder Bay Road.

[1] Australian Defence activity began in this area of Sydney Harbour as early as 1803 when a gun battery was installed on Georges Head.

This is the oldest remaining colonial fortification in Australia and was built to defend the entrance to Sydney Harbour during the Napoleonic wars.

[citation needed] On 10 March 1801 Governor Philip Gidley King informed the Secretary of State for Colonies that a battery was "in forwardness opposite the entrance to the Harbour, which will completely prevent attack from without".

The departure of British forces put the onus on colonies like New South Wales and Victoria to assist in, and organize its own defences, prior to the Federation of Australia.

The fort held a prominent position and was located high above sea level with strategic views to the entrance of Port Jackson.

[citation needed] Defence tactics were planned using telescopes and plotters mounted in the middle of the second gun pit.

[citation needed] In 1888 Georges Head was chosen as the best place to observe and fire underwater mines, the latest in harbour defences.

Minefields were laid across the main shipping channels of Port Jackson from 1876 to 1922 and a base was built at Chowder Bay for the submarine miners.

The boom net spanned the entire width of Sydney Harbour from Green (Laings) Point, Watsons Bay to Georges Heights in Mosman.

[2][11] The hospital was carved out of solid rock during the construction of the tunnel system in 1872, and was originally designed to provide a storage room for the black powder charge used when firing the 68-pounder and 80-pounder guns of the battery.

[12] Georges Heights and in particular the Officer's mess precinct is culturally significant for the important role it played in the strategic defence of Sydney.

Alterations to the A84 Battery show the continual evolution and development of defensive systems and the application of the most modern technology and building techniques.

The site is valued by the local community and Defence personnel for its role as a vantage point and as a gateway to the harbour.