Georges Head Battery The Georges Head Battery consists of the original battery and barracks 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 , Georges Head in the suburb of Mosman in Sydney , New South Wales , Australia . The Georges Head battery is one of three forts in the area that were built for the purpose of defending the outer harbour . The other two forts are located at Middle Head and Bradleys Head , Mosman . The fort became a command post in the 1890s for the coordination of all of Sydney ' s harbour defences . History . 1870s . Georges Head battery was built in 1871 after the removal of the British forces from Australia in 1870 . Their departure put the onus on wealthy colonies like New South Wales and Victoria to assist in , and organize its own defences . Georges Head Battery was an outer line harbour defence fortification designed especially to attack and prevent enemy ships from infiltrating the inner harbour . The fort held a prominent position and was located high above sea level with strategic views to the entrance ( Sydney Heads ) of Port Jackson . Other batteries were located on Middle Head , South Head , Shark Point and Bradleys Head , but none were ever used for combative purposes . Georges Head was armed with four 80 pounder rifled muzzle loading guns and two 68 pounder muzzle - loading guns . It took three months and 250 soldiers to roll the gun barrels all the way from North Sydney to the batteries . They came along a rough track which later became Military Road . The guns had been positioned so poorly that this created the risk of one gun firing upon another . Also , the guns and soldiers were visible from the harbour . In 1877 large mounds of earth were placed between the pits to make sure the guns could not fire upon each other and to help protect the gun crew from enemy fire . When construction of the fort was complete , there were a total of 41 gun emplacements positioned around the harbour . Defence tactics were planned using telescopes and plotters mounted in the middle of the second gun pit . From the telephone exchange , the Port Jackson District Commandant could communicate with all military installations on the harbour . Telephone cables ran through the tunnels , down the cliff and under the harbour to batteries on the other side . 1880s . In 1888 Georges Head was chosen as the best place to observe and fire underwater mines , the latest in harbour defences . Each underwater mine was attached to an electric cable that ran up the cliff to a firing post . From there , miners watched for ships entering the harbour . The miners ' job was to explode the mine closest to an approaching enemy ship . 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 work of the submarine miner was secretive , technical and dangerous . During a demonstration in 1891 , a crowd of several thousand watched as a terrible accident killed four miners and injured another eight . World War II . In 1942 , during the Second World War , the ' Sydney Harbour anti - submarine boom net ' was installed . The boom net spanned the entire width of Sydney Harbour from Green ( Laings ) Point , Watsons Bay to Georges Heights in Mosman The command post remained until the 1930s . The area then became home to various defence bases until 2002 when the Army left after 130 years at Georges Head . The area in which the fortifications are situated is now open to the public and the Harbour Trust has restored the historic fortifications , creating a new type of lookout . Casualty clearing station & storage facility . 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 . The floor was originally covered in a bituminous substance , the walls were tiled with ceramic tiles not unlike those seen on the wall pictured , and the tunnel ceiling leading to the room was lined with cork . The purpose of these measures was to reduce the possibility of sparks and the potential for a powder explosion . The zigzag tunnel at the far end of the room was designed to act as a blast wall to contain any blast within the immediate area . The room has been modified since 1872 and was used as a casualty clearing station in 1932 / 33 when the battery was re - gunned with the 6 inch breech loaded MK7 guns . Designed for emergencies only , it fortunately saw no casualties of war .