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Wet Landing at Morotai
Wet Landing at Morotai
bigpigeon.us webpage WWII Japan > New Guinea > Western New Guinea, © 2026 by Robert A. Christiansen, updated by RAC 28 Dec 2025

This page summarizes the drive westward along the New Guinea North Coast, advancing towards the Philippines, April–September 1944.
By early 1944, US combat operations in the South Pacific Area were winding down. The South Pacific Area commander, Admiral William Halsey, left to assume command of the US main battle fleet, known interchangably as the Fifth Fleet and the Third Fleet. Some South Pacific forces such as the Thirteenth Air Force were transferred to the Southwest Pacific Area.

By April 1944, General MacArthur's Southwest Pacific Area forces - land, sea and air - were powerful enough and Japanese sea and air forces sufficiently weakened for major changes in Allied operations in New Guinea. ​

During the period of April to September 1944, Southwest Pacific Area forces launches a bold series of westward advances along the north coast of New Guinea, ending with a landing on the island of Morotai in the Netherlands Indies, as shown on the accompanying maps.  These amphibious landings positioned US forces for the first landing, on Leyte, in the Liberation of the Philippines.

​MacArthur's Sixth Army bypassed a large  Japanese troop concentration in the Wewak area on the north coast of New Guinea and launched multiple operations in quick succession.

During this period, Australian combat forces were released from participating in offensive operations and either returned to Australia to regroup and train or engaged in rear area mopping-up duties.
​
1944 New Guinea Offensives
1944 New Guinea and Bismarck Archipelago Offensives
S & SW Pacific Western New GuineaA Second View of Western New Guinea Operations
Below are outlined in chronological order the US operations in the Western New Guinea area. I believe only the Battle of Hollandia, the Battle of Lone Tree Hill, the Battle of Biak and the Battle of Driniumor River cost more than 100 American lives.
The Battle of Hollandia, 22-26 April 1944
​Hollandia, now a city in Indonesia known as Jayapura, offered the best harbor for hundreds of miles along the north coast of New Guinea, as well as several airfields.

The large-scale Hollandia landings by the 24th and 41st Infantry Divisions were successful, but bypassed a concentration of Japanese troops in the Wewak area over 200 miles to the east.

Around 157 US military died in the Battle of Hollandia.

During the liberation of the Philippines, Hollandia served as a major rear-area base.
The Battle of Hollandia
The Battle of Hollandia
The Landing at Aitape, 22 Apr - 2 May 1944
Aitape is about halfway between Hollandia and Wewak.
To help protect Hollandia from the Japanese 18th Army to the east at Wewak, elements of the 41st Infantry Division landed at Aitape on 22 April, and soon secured the area.

Aitape had the advantage of a nearby airfield.

In mid-July, the Japanese 18th Army did attack, leading to the long Battle of the Driniumor River. The river is shown on the right of the accompanying map.
The Aitape Area
The Aitape Area
The Battle of Wadke, 17-21 May 1944 and The Battle of Lone Tree Hill, 17 May - 2 Sep 1944
The tiny Wadke Islands lie just off the New Guinea coast, 120 miles west of Hollandia. The US Sixth Army wanted to occupy the Wadke area in order to:
  • Use the Wadke airfield to support pending operations further west in New Guinea.
  • Use Maffin Bay, about ten miles west of Wadke, as a staging area for subsequent amphibious operations to the west.
Unfortunately a large pocket of Japanese troops, possibly as many as 15,000 occupied the  New Guinea coastal area near Maffi Bay.
Elements of the 41st Infantry Division landed on the New Guinea coast across from Wadke on 17 May. The following day Wadke was invaded, and after a four-day battle  Wadke was secure. The Wadke airfield was quickly put in service. Around 40 US military died in the Battle of Wadke.

Japanese forces established a strong defensive line in the high ground east of the Woske River. The north anchor of this line was the so-called Lone Tree Hill, located between the beach and the coastal track. Not until the end of June was Lone Tree Hill secure, although Japanese forces remained on the west side of the Woske River. Over 400 US military died in the protracted Battle of Lone Tree Hill, which was arbitrarily declared over on 2 September 1944.
Maffin Bay Area
Maffin Bay Area Apr 1944
Wadke Area
Wadke Islands and the Surrounding Area
The Battle of Biak, 27 May - 20 Aug 1944
Because of the airfields on its south shore, the island of Biak was chosen for an amphibious landing by the reinforced 41st Infantry Division.

​Unfortunately intelligence had underestimated the number of defenders. Moreover, cliffs containing fortified positions lay to the north of the airfields.

The result was a long and difficult battle on a steaming jungle island, with 460 American dead, with isolated Japanese resistance continuing after the island was declared secured on 20 August.

​
The Battle of Biak
The Battle of Biak
The Battle of Noemfoor, 2 Jul - 31 Aug 1944
Because of the unexpected lack of progress early in the  Battle of Biak, the Southwest Pacific Area command began planning a parallel invasion of Noemfoor Island to the west of Biak. Noemfoor also had several airstrips on the west and north shore, along with a much smaller Japanese garrison.

The first Allied aircraft began landing on Noemfoor on July 6. Noemfoor was secured on 7 July although isolated Japanese pockets remained in the interior and east.

66 Allied troops were killed on Noemfoor. 
Noemfoor & Biak
Noemfoor & Biak
The Battle of the Driniumor River, 10 Jul - 25 Aug 1944
The Battle of Driniumor River was a defensive battle just east of Ataipe. The battle  prevented the Japanese 18th Army troops, bypassed earlier in the Wewak area, from breaking through US lines.

The accompanying map shows positions at the beginning of the Battle of the Driniumor River. I have included this map because it shows the location of Troop F of the 112th Cavalry Regiment, which included my son-in-law's father, Lloyd Joyce.

The Battle of Drinumor River left a much-weakened Japanese army in the Wewak area, at the cost of 440 Americans dead. 
The Vogelkop Peninsula
Elements of the 6th Infantry Division landed on the Vogelkop Peninsula at the western end of New Guinea on 30 July 1944. Over the next month, they encountered little opposition, losing only 14 dead.

On the adjoining map, note the bomber base at Mar, sometimes called Sansapor Airfield, and the fighter base on Middleburg Island. These were used by the Thirteenth Air Force to conduct raids over Celebes in the Netherlands Indies.
Vogelkop Operation
Operations near Sansapor on the Vogelkop Peninsula, Netherlands New Guinea
Morotai - 15 September 1944
The island of Morotai lies in today's Indonesia between the western tip of New Guinea and the south end of the Philippines island of Mindinao. Morotai appears in the upper right of the accompanying  map.

When MacArthur's 31st Infantry Division invaded Morotai, Morotai was lightly defended, most area Japanese forces being on the nearby island of Halmahera.
Indonesia as of 2018
Indonesia, formerly the Dutch East Indies, as of 2018
Morotai was developed into a major air base, but a Japanese military presence on the island remained. PT boats interdicted nighttime Japanese barge traffic that brought supplies and reinforcements from Halmahera to Morotai.

When the War with Japan ended, 660 Japanese troops remained on Morotai and 40,000 on Halmahera.
Sources for Big Pigeon's WW II Japan > New Guinea > Western New Guinea webpage:
Pottawattamie County, Iowa area WWII Dead - WWII Japan > New Guinea > Western New Guinea: 05-08 - WWII Japan > New Guinea > Western New Guinea: (four dead, updated 5 Nov 2025)
​​† Amunson, Leo Victor, SN 37-037-849, US Army Air Force, Monona Co. (St Paul's
  • Co. B, 46th Engineering Construction Bn.; battalion was enlarging airfields while ground combat continued on Biak Is., Netherlands Indies; WIA Jul 1944; stepped on an antipersonnel land mine; DOW in hospital 28 Jul 1944.
  • WWII Japan > New Guinea > Western New Guinea @ Battle of Biak Island
† Christensen, Dale Eldon, SN O-2-036049, US Army, Audubon Co.
  • Troop E, 112th Cavalry Regt.; KIA 4 Aug 1944 near Afua, New Guinea.
  • WWII Japan > South & SW Pacific > Western New Guinea @ Battle of the Driniumor River
† Linder, Gerald Edward, SN O-378126, US Navy, Montgomery Co.
  • Destroyer USS Kalk (DD-611), Seventh Fleet; KIA 12 Jun 1944 off southern coast of Biak Is., W. of Hollandia, Dutch New Guinea; Kalk hit by Japanese bomb while escorting LSTs from Hollandia, New Guinea to Biak; thirty dead, 40 wounded, Kalk survived; BNR.
  • WWII Japan > South & SW Pacific > Western New Guinea @ Battle of Biak
† Shipman, Fred Howard, SN 17-178-496, US Army Air Force, Harrison Co.
  • 836th Engineering Aviation Bn.; KIA 19 May 1944 Wadke Is., W of Hollandia, Dutch New Guinea.
  • WWII Japan > South & SW Pacific > Western New Guinea @ Battle of Wadke