The Battle of Dumpu was an action fought in September and October 1943 between Australian and Japanese forces in New Guinea during the Markham, Ramu and Finisterre campaigns of World War II.

[1][2] In the wake of the landing at Nadzab on 5 September 1943, and the subsequent capture of Lae on 16 September, Major General George Alan Vasey's 7th Division moved on to the next task assigned by the Commander in Chief, South West Pacific Area, General Douglas MacArthur, in the June 1943 directive that outlined Operation Cartwheel.

[3] At the Battle of Kaiapit on 20 September, the 2/6th Independent Company won a stunning victory against a numerically superior Japanese force.

There was some debate amongst the air and engineer generals about the relative merits of airfield sites around Kaiapit and Marasawa, but Vasey intended to seize them all in any case.

[9] The rebuff at Kaiapit and the landing at Finschhafen on 22 September caused Lieutenant General Hatazō Adachi, the commander of the Japanese Eighteenth Army (and therefore Herring's opposite number) to change his plans.

He had originally intended that the 51st Division would retire from Lae along the southern slopes of the Finisterre Range, through Kaiapit, and thence into the upper Ramu Valley; but Vasey had anticipated this, and had blocked the route.

The 51st Division's commander, Lieutenant General Hidemitsu Nakano, then decided to withdraw over the steep and rugged Saruwaged Range.

[10] Lieutenant Colonel F. H. Sublet's 2/16th Infantry Battalion, a unit from Western Australia, arrived at Kaiapit on 22 September.

Only one saw any, the 12 Platoon, under Lieutenant J. R. Walder, which spotted three Japanese soldiers on the far side of the Umi River who fled when fired upon.

A. Bishop, arrived at Kaiapit on the morning of 23 September, having flown directly from Jacksons and Wards at Port Moresby in 45 USAAF C-47 transport aircraft, escorted by P-47 Thunderbolt, P-38 Lightning and P-39 Airacobra fighters.

[12] No aircraft arrived on 24 September, leaving Dougherty without the 2/14th Infantry Battalion, which was still back at Nadzab, and with only the rations and ammunition that the 2/16th and 2/27th had brought with them.

[15] The pioneer platoon of the 2/16th strung a rope across the Umi River, allowing the heavily equipped diggers of B and C Companies to cross the fast-flowing torrent.

Lieutenant Everette E. Frazier, an American aviation engineer, pegged out a landing strip nearby and had it ready to receive C-47s in four hours.

He explained that the reason for halting the 2/16th was an appreciation that Adachi would persist with his original plan, known to the Australians through documents captured at Kaiapit, even though it had been overtaken by events.

Vasey believed that the open area between the Umi and Kaiapit would be an excellent place to destroy the Japanese force, should it choose to attack.

He therefore proposed to halt for a while, reinforcing the position at Kaiapit with Brigadier Kenneth Eather's 25th Infantry Brigade rather than displacing it forward as originally intended.

Dougherty flew over the area in a Douglas SBD Dauntless, and concurred with Vasey's assessment of the ground, although not with his appreciation of the enemy's intent.

Part of the problem was that the Fifth Air Force restricted landings at Kaiapit to between 09:00 and 15:30 the previous day in order to conserve fighters.

Vasey was informed that the construction of the Markham Valley Road from Lae to Nadzab and operations around Finschhafen had priority, and his 18th Infantry Brigade would not be flown in except in the event of an emergency.

Six jeeps hauled rations, four carried the brigade headquarters and signals, three brought the 2/6th Field Ambulance, and two towed 25 pounders.

The jeeps and light guns were dragged across the Umi, leaving three behind to form a shuttle service that moved stores from Kaiapit.

[20][23] By this time, Herring knew that the rest of the Japanese 20th Division was on the Rai Coast and not in the Marawasa area, so Vasey was opposed only by its 78th Infantry Regiment.

[25] Although native porters were engaged to bring rations forward to the troops, the 2/16th and 2/27th advanced so fast on 1 October that stores had to be dropped by air.

It was then found that the road on the far side was impassable, so a bypass was made, allowing them to move to an area near Arafagan Creek, on the banks of the Ramu River.

[20] The 21st Infantry Brigade set out again on 4 October, with Lieutenant Colonel Ralph Honner's 2/14th heading for Wampun while the 2/16th advanced on Dumpu,[27] crossing the Gusap on a bridge that had been built the previous day.

[29] Honner found that the native porters accompanying his battalion had no water, and were therefore not only thirsty, but hungry as well, as they could not cook their rice rations.

The Japanese sent out patrols to find the two men, and they fired into the kunai grass where he was hiding, wounding him again, this time in the left hand.

[30][31] Pryor reached D Company, whose commander, Captain G. O. O'Day, immediately set out with Lieutenant A. R. Avery's 16 Platoon.

[32] An airstrip was developed at Dumpu, which would assume great importance in the logistical support of the subsequent fighting in the Finisterres.

The base at Gusap "paid for itself many times over in the quantity of Japanese aircraft, equipment and personnel destroyed by Allied attack missions projected from it".