The battalion moved to Tenterfield, New South Wales in early May after which personnel from Queensland and New South Wales were granted home leave. Later in the month, a further move to Kilcoy, Queensland, occurred after which jungle training began. In August 1942, the 2/12th Battalion was transported to Brisbane where it embarked upon the transports "Anshun" and "Jacob", bound for New Guinea. They were subsequently deployed to Milne Bay, where they took part in the Australian counterattack following the Japanese landing, which resulted in the first major defeat of the Japanese of the war. In October, under the command of Lieutenant Colonel Arthur Arnold, the battalion was selected to invade Goodenough Island. Transported aboard the destroyers HMAS "Stuart" and "Arunta", after a short fight the battalion secured the island. They subsequently remained on Goodenough Island until December. In late December, they were re-committed to the fighting, as the understrength 18th Brigade was sent to Buna, where the 2/12th successfully attacked Giropa Point on New Years Day 1943, despite losing 63 men killed and 122 wounded. After this, the battalion took part in further actions around Sanananda, where they suffered a further 61 men killed in action. The battalion's involvement in the fighting lasted until late January 1943 when it was withdrawn to Soputa by road, and then by air to Port Moresby. In early March, the battalion returned to Australia aboard the transports "Taroona" and "Maetsuycker".