[1] Prior to the entry of Japan into World War II in early December 1941 it was the policy of Military Command in New South Wales to give priority to the fortification of the industrial areas of Newcastle, Sydney and Port Kembla.

The Small Arms Factory had been constructed as a central defence arsenal between 1909 and 1911 as part of Australia's general movement towards self sufficiency following Federation in 1901.

This dictated the placement of one Heavy Anti Aircraft Gun Station (A Troop) at the western end of the valley at South Bowenfels and the other Heavy Anti Aircraft Gun Station (B Troop) at the eastern end of the valley on the heights of Scenic Hill overlooking the Vale of Clwydd.

[1] Work began on the stations immediately and workmen from the Water Conservation and Irrigation Commission poured the concrete floors of the emplacements prior to 22 December 1941.

The urgency for completion of the gun stations increased as the Japanese moved through Malaya, Singapore and finally to various islands north of Australia.

The Command Post was centrally located among the four gun emplacements and was, according to Southall, of a World War I blockhouse design.

From the central room of the blockhouse protected passages gave access to the platforms containing the tracking instruments: the Predictor on the roof of the octagonal section of the Command Post and the Barr & Stroud Height Range Finder and the Telescope (or Toc 1).

[1] The Predictor, manned by six gunners, was manufactured by Vickers in England and was the equivalent of a computer which determined the direction and speed of travel of the enemy aircraft and the time of flight for the projectile fuse setting.

[6][1] There were over 100 static Anti Aircraft Gun Station sites for defence against air attack were established in Australia during World War II.

During World War II the accuracy of bombing was limited to the skill of the aircrew and the higher the bombers were flying the less likely they would hit their target.

[5][1] The main equipment of the Heavy Anti Aircraft artillery was the 3.7 inch anti-aircraft gun which came in two versions, static and mobile.

The main difference between the two types of gun was that the mobile has the outrigger legs and the static was bolted to the ground and had a large arm atop to counter the weight of the barrel being slightly further forward of the point of balance.

The guns were located in revetments built to trunnion height and laid out in a shallow arc of about 90 degrees close to and easily seen from the Command Post.

[1] The two stations include four octagonal reinforced concrete gun emplacements for 3.7 heavy anti-aircraft guns arranged around a central reinforced concrete command bunker consisting of a square, three level building connected to a smaller two level octagonal building.

Concrete revetments which form ammunition storage bays and provided protection from bomb blasts are built into the main walls on alternate sides of the octagon.

All three appear to be in good condition when viewed by the casual observer, however they are in need of some conservation and ongoing maintenance works to arrest rust and other forms of deterioration resulting from exposure to the weather.

Raised octagonal cement platforms with a central iron pipe located in the centre cut off to the height of the platform are located on a larger circular base appearing to consist of sand, cement, slag and other materials that have now broken down to form a loose surface that has deteriorated significantly.

The Scenic Hill Gun Station has suffered significant subsidence resulting in partial collapse in some areas and nature has begun to reclaim the site.

The emplacements were introduced as an important part of the network of defence sites established at Lithgow during the latter half of World War II.

This is further demonstrated by the construction of the dummy batteries to ensure local defence facilities were not easily targeted during an enemy attack.

The Bowenfels and Scenic Hill Anti Aircraft Gun Stations and the Scenic Hill Dummy Anti Aircraft Gun Stations have state historical significance as an important part of the World War II network of defences of Lithgow established during the War to defend the important mining, manufacturing and transport hub located there, in particular the Small Arms Factory.

The construction of the stations and the associated dummy stations, farm and villages in the Lithgow area demonstrates the increased perception of the threat of the enemy to Australian inland industries and defence sites when Japan entered the war and concerns regarding Japan's ability to reach Australian shores.

One of a series of World War II anti aircraft defence sites developed in NSW from Newcastle to Port Kembla and of a limited number constructed inland from 1941.

[1] This Wikipedia article was originally based on Lithgow Heavy Anti Aircraft Gun Stations and Dummy Station, entry number 01862 in the New South Wales State Heritage Register published by the State of New South Wales (Department of Planning and Environment) 2018 under CC-BY 4.0 licence, accessed on 2 June 2018.