 Lithgow was included as an adjunct to the Sydney Fortress Area in order to place its industries, transport infrastructure and defence site under protection from aerial attack, including the Small Arms Factory in the centre of Lithgow, the ammunition depots at Clarence and other railway tunnels, the major depot at and the various coal mines in the Lithgow Valley and nearby.Sydney Command was particularly concerned about attack from the high level Japanese bombers and low level strafing fighter planes or dive bombers.The Army Command inspection of December recommended the defences take the form of two 4-gun 3.7 inch anti-aircraft batteries plus a Lewis Machine Gun detachment for the close defence of the Lithgow Small Arms Factory.