Code-named Operation POSTERN, the airborne insertion was a pincer attack, aimed at seizing the port of Lae and the airfield at Nadzab to support future allied operations in Papua New Guinea.
On 4 September 1943, the 9th Australian Division staged an amphibious landing east of Lae. This landing was the first amphibious assault by Australian forces since Gallipoli. On 5 September 1943 and in support of the amphibious landing, elements of the 7th Australian Division conducted an airborne insertion at Nadzab with the US 503rd Parachute Infantry Regiment.
At the time of the amphibious and airborne landings, Japanese forces were focussed on the defence of their smaller base at Salamaua which was also under attack by Australian and US forces, who later captured the base on 11 September 1943.
As the US 503rd Parachute Infantry Regiment had no artillery, the Commanding Officer of the Australian 2/4th Field Regiment offered soldiers from his Regiment, as well as two short 25 Pounder field guns (a cut down version of the 25 Pounder for jungle warfare). Thirty four volunteers were selected from the 2/4th Field Regiment and received intensive training from the American paratroopers. On 30 August 1943, a practice jump was carried out and three members were injured. The replacement personnel, as well as some who had missed the training jump, carried out their first jump in action at Nadzab.
Prior to the airborne landing, Australian and Papuan infantry personnel patrolled the area and confirmed that no enemy troops were south of the Markham River. A force of Australian Engineers from the 2/6th Field Company and Pioneers from the 2/2nd Pioneer Battalion, supported by native carriers, moved overland and by river to the Markham River near Nadzab. Here they prepared a crossing, and once the paratroops had landed, moved to Nadzab to prepare the airfield for the fly in.
Leading the aircraft fleet at 1000 feet, were six squadrons of B-25 Mitchell bombers, each with eight 50” machine guns in the nose and 60 fragmentation bombs in the bomb bay. Their task was to strafe and bomb all the drop zone areas.
Immediately behind and about 500 feet above were the Mitchell bombers, with six A-20 Havocs flying in pairs. Their role was to lay a smoke screen as the last fragmentation bomb exploded.
Behind the A-20s came 96 C-47 Dakotas transporting paratroops, supplies and artillery. The C-47s flew in three columns of three planes, each column carrying a Battalion set up for a particular dropping zone.
One hundred and forty six US fighters (P-38 Lightnings, P-39 Airacobras and P-47 Thunderbolts) were used to protect the Dakotas.
Following the transports, came five B-17 Fortress bombers acting as mobile supply units and
loaded with 3000 pound packages to be dropped by parachute to the paratroops as they needed them. The B-17 Fortress bombers stayed over Nadzab practically all day, dropping a total of 15 tons of supplies in this manner.
Behind the supply B-17s was a group of 24 B-24 Liberator bombers and four B-17s. These aircraft left the column just before the junction of the Watut and the Markham Rivers to attack Japanese defensive positions at Heath’s Plantation, about half way between Nadzab and Lae.
Five weather aircraft were used prior to and during the fly in along the route, to keep the units updated on weather during the flight to the rendezvous.
Simultaneously ten Beauforts, five Bostons, and seven P-40 Kittyhawk fighters from 100, 22 and 76 Squadrons of the Royal Australian Air Force, attacked the Japanese refuelling field at Gamsata rendering it out of action.
As a result of the supporting air actions, no Japanese aircraft intercepted the drop of the paratroops. The 7th Australian Division commenced flying in to Nadzab on 6 September 1943.
The Australian Commander in the South West Pacific Area, Field Marshal Sir Thomas Blamey declared the capture of Lae and Salamaua to be "a signal step on the road to Victory". The airborne insertion at Nadzab influenced broader thinking about the value of airborne operations.