 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.The defences were introduced to protect Lithgow's important mining, manufacturing and transport industries and the Lithgow Small Arms Factory.The construction of these defence facilities together with those at the Small Arms Factory represents a changing national defence policy in response to the entry of Japan into World War II, and an increased perception of the vulnerability of inland areas brought about by improvements in aircraft technology.