Green Hill Fort. Australia was constructed between 1891 and 1893 to mount three 6-inch BL guns. One of these guns was a Mark IV and the other two Mark VI versions. The armament included a 0.45-inch Maxim Machine Gun
As with many other fortifications of this period, the conception for the Fort came from Colonel Sir William Jervois, and his assistant Lieutenant-Colonel Peter H Scratchily. Fort Scratchely in Newcastle was named after this officer.The actual building of the fort was done by Major Edward Druitt, a Royal Engineer based in Queensland. The role of the battery was to protect Port Kennedy and the coal hulks moored there.
The Fort was similar in many ways to the Mobilization Centres built around London at about the same time. Earth ramparts with a fire step, compact magazine and not barrack accommodation. The Fort however was very exposed, having no natural vegetation to conceal the position. See plan image.
A small barracks was built on the hill immediately adjacent to the fort. Only traces of these barracks can now be found.
In 1897 a single 4.7-inch QF was mount on Milman Hill. Millman Battery was to extend the effective coverage of the anchorage defences.
In 1904 both Green Hill Fort and Millman Battery remained active and the duties of the garrison including protecting the landing point for the undersea cables. The total military force on the Island of all ranks was 307.