Allocated to the 23rd Brigade of the 8th Division, after initial training it was sent north to Darwin in September to construct defences around the Adelaide River and Noonamah amidst concerns about Japanese intentions in the Pacific. While most of the division deployed to Malaya, the 2/4th remained behind and following the Japanese entry into the war, the battalion was allocated to bolster the garrison at Koepang as part of Sparrow Force on Timor. An advanced party was sent to the island in early February 1942, and on 14 February the rest of the battalion followed; however, the convoy in which they were embarked was attacked by Japanese aircraft and it was turned back. Returning to Darwin, the majority of the 2/4th’s equipment was lost when the ship carrying it was sunk in Darwin harbour during a Japanese air attack on 19 February. Consequently, the battalion’s deployment was cancelled and it remained in the north for more than a year, during which time they undertook defensive duties to counter the threat of Japanese invasion. During this time, the battalion was commanded by Lieutenant Colonel John McCarty. In November 1942, the battalion was reassigned to the 3rd Brigade, a Militia formation that had been mobilised for full-time service and sent to the Northern Territory earlier in the year to bolster the field force there.