In 1889 the military forts at Middle Head held large 6-inch guns on ‘disappearing’ carriages which recoiled into a pit to be reloaded. Watch this animation to see how the guns were designed to protect Sydney Harbour.

Outer Middle Head changed as technology improved. 1877 saw the arrival of British military advisers Governor Sir William F.D. Jervois and Lieutenant-Colonel Peter Scratchley. Their job was to assist Australia and New Zealand to coordinate their defences on behalf of the British Empire.

The small muzzle loading guns were removed and replaced with very large guns – 10 inch, 18 ton rifled muzzle loaders. Electricity was connected to the fort and communications were improved.

From 1885 the Middle Head area became part of the School of Artillery where people trained to use the guns and transport them.

During the First World War (WW1) older installations were decommissioned and replaced with newer guns. In the 1940s, with the onset of the Second World War (WW2) and fears of invasion, construction went full steam ahead, often without adequate planning or materials.

New guns and technology were installed. The Central Control building was extended, radar was installed, and the fort was manned 24/7 to watch for foreign objects entering the headlands.

There were many dangers for the men who operated the guns – even during training and injuries were not uncommon. The sound and vibration of the guns exploding when fired could lead to loss of consciousness and loss of hearing known as 'gunners' ear.

After WW2 the military had limited use for these fortifications. However, specialist training was carried out during the 1950s and 1960s in the subterranean tunnels and rooms.

The former engine room became known as the 'tiger cages'. Men in training were 'abducted' and spent several days undergoing conditions they could have faced if captured during active overseas duty.