In the early 1930’s the 40 mm gun was developed for defence against low flying aircraft by the Swedish Armament Manufacturer ‘Bofors’. The 40mm Bofors was an extremely versatile gun. Apart from its prime role it was used as an anti-tank weapon, against torpedo-boats in harbour defence, in neutralising fire during infantry assaults, for attacking fortified bunkers, shooting up enemy transport and indicating lines and timing of infantry advance at night.

When the 2nd AIF arrived in the Middle East two of the Anti Aircraft Regiments were trained on and issued with 40 mm Bofors guns. On their return to Australia they brought their guns with them in most cases providing the Anti Aircraft protection for their transport ships.

The Army in Australia was issued with the 40 mm Bofors gun in late 1941 and gradually batteries were built up and sent to areas where they might be required. These batteries and those of the AIF saw action in all theatres of the war, in Darwin and the South West Pacific Area.