At the outbreak of the Second World War, A Field Battery came under the command of the School of Artillery, Holsworthy, in their mobilization role as Depot Battery. However, in August 1943, A Field Battery was reorganized to form the 2nd Australian Mountain Battery, following the successful involvement of the 1st Mountain Battery during operations around Buna and Wau. Equipped with 75 mm pack howitzers, under the command of Major William Stevenson the 2nd Mountain Battery arrived in New Guinea in September of that year, initially based around Port Moresby with the 3rd Division. In November, the battery was transferred to the 9th Division to provide support around Finschhafen. In early 1944, the battery moved to Lae and was re-assigned to support the 7th Division in the Finisterre Ranges, where its operations were hampered due to limited transport in the difficult terrain. The battery was moved to Dumpu in April 1944, where it came under the command of the 11th Division, before moving to Lae in May.