When the Korean War broke out on 25 June 1950, No. 77 (Fighter) Squadron of the Royal Australian Air Force (RAAF) was based at Iwakuni, Japan, having served with the British Commonwealth Occupation Force (BCOF) for four years. Equipped primarily with North American P-51 Mustangs, the squadron also operated a communications flight of two Douglas C-47 Dakotas and two Austers. Personnel were preparing to return to Australia when they were placed on standby for action over Korea; the Mustangs began flying missions as part of United Nations Command (UNC) forces a week later. Following the landing at Inchon and the consequent advance northward of UNC troops, No. 77 Squadron relocated to Pohang, South Korea, on 12 October 1950. It left behind its main support elements at Iwakuni. No. 91 (Composite) Wing was established at the base on 20 October and given administrative responsibility for all RAAF units operating during the conflict. As well as No. 77 Squadron, this included the newly formed No. 391 (Base) Squadron and No. 491 (Maintenance) Squadron, and No. 30 Communications Flight, formerly the No. 77 Squadron Communications Flight. The flight's original complement of two Dakotas and two Austers had been augmented in September 1950 by two more Dakotas from Australia. On 1 November, the flight was designated No. 30 Communications Unit.