bigpigeon.us webpage WW II - Japan > South & SW Pacific > New Guinea, updated by RAC 7 Oct '19.      Not yet complete.
Between 1942 and 1945, Australian and American forces fought a ground war on the island of New Guinea against Japanese invaders. I find I best understand this complex series of operations if I break it up into nine campaigns or battles.
 1 and 2 - The Kokoda Track and Milne Bay, Summer 1942
The first two actions against Japanese invaders in New Guinea were fought by Australian forces in the summer of 1942 with only a small US contribution. 
  1. A land attack on Port Moresby  from the Buna area via the Kokoda Track.
  2. An amphibious invasion of Milne Bay on the eastern tip of New Guinea.
In both instances, Australian forces repelled these Japanese efforts to advance further into New Guinea.

If I add more about these actions, it will be on the Japan Overreaches webpage.

Australian forces harassed the Japanese by land and air as  they retreated north on the Kokoda Track back towards the Buna area.
The Kokoda Track
The Kokoda Track
3 - The Buna-Gona-Sanananda Campaign 16 Nov '42 - 22 Jan '43
This first Allied offensive on New Guinea was a joint Australian-US venture. The intent was to clear the Papuan Peninsula (the far eastern tail of New Guinea) of Japanese forces who had established enclaves in the Spring of 1942 at Gona, Sanananda and Buna on the northern coast of New Guinea.

The Buna-Gona-Sanananda Campaign was poorly planned and poorly resourced and fought over difficult swampy terrain by American troops untrained in jungle warfare. I believe it was likely pushed forward faster than it should have been for political reasons.

After a promising start, the campaign floundered in late November, with progress resuming in January. Especially troublesome were the strongpoints marked with circles on the track from Soputa to Sanananda Point. 
At one of these strongpoints, two men from Pottawattamie County, members of the same company, died on 15 January.
4 - The Lae-Salamaua Campaign, 22 Apr '43 - 16 Sep '43
Still to do!

Only Australian troops were involved in the early stages of this campaign. 

Prior to the beginning of the Allied Lae-Salamaua Campaign, the Japanese attempted to move 6,900 troops from Rabaul to the Lae area. In the ensuing Battle of the Bismarck See, nearly 3,000 of these troops were killed. Allied losses totalled 13.
5 - The Huon Peninsula Campaign, 22 Sep '43 - 1 Mar '44
Still to do!

​
The Final Phase of the New Guinea Campaign
By April 1944, General MacArthur's Southwest Pacific forces - land, sea and air - were powerful enough and Japanese sea and air forces weak enough for major changes in Allied operations in New Guinea. 

​Macarthur began to bypass some Japanese troop concentrations on the north coast of New Guinea and to launch multiple operations in quick succession. Australian combat forces were also released from participating in offensives and either sent back to Australia for retraining or assigned to rear area mopping-up duties.
 1944 US New Guinea Offensives1944 New Guinea US Offensives
6 - The Hollandia and Aitape Landings
The large-scale Hollandia and Aitape landings on 22 April 1944 were successful, but bypassed concentrations of Japanese troops, especially in the Wewak area.
7 - The Battle of the Driniumor River, 10 Jul - 25 Aug '44
The Battle of Driniumor River was a defensive battle, preventing Japanese troops bypassed earlier from breaking through US lines and passing on to the west.

The accompanying map shows positions at the beginning of the Battle of the Driniumor River and is included because it shows the location of Troop F of the 112th Cavalry Regiment, the troop of my son-in-law's father, Lloyd Joyce.
8 - The Western New Guinea Landings 
Still to do!
Sources for the WW II -  New Guinea webpage
  • The webpage header photo The Beach at Buna is courtesy of time.com and first appeared in the 20 Sep 1943 issue of LIFE magazine.
  • The Kokoda Track map is courtesy of pinterest.com.
  • The Map depicting the approach of the Allied forces overland ... is courtesy of https://anzacportal.dva.gov.au/.
  • The Road Block Positions, Sanananda map was found at https://en.wikipedia.org/wiki/41st_Infantry_Division_(United_States)#/media/File:Sanananda_Roadblocks.jpg
  • The 1944 New Guinea US Offensives map was found at https://history.army.mil/books/wwii/MacArthur%20Reports/MacArthur%20V1/Images/p_039.jpg
  • The Driniumor Line map is courtesy of https://www.ibiblio.org/hyperwar/USA/USA-P-Approach/maps/USA-P-Approach-7.jpg.
  • http://www.historyofwar.org/articles/campaign_new_guinea.html is a well-written report of WW II in New Guinea.
Pottawattamie County, Iowa WW II Dead - New Guinea
(taken from the bigpigeon.us WW II Dead webarea)
05-03 - South & Southwest Pacific - New Guinea: (nine dead, updated 27 Apr 2020)
† Porter, John L. Jr. - SN 39-125-170, US Army
187th Airborne Regt., 11th Airborne Div.; WIA New Guinea; DOW 25 Oct 1944, San Mateo Co., CA.
† Profeda, Louis Anthony - SN 37-139-285, US Army
Co. M, 128th Inf. Regt., 32nd Inf. Div.; KIA 22 Nov 1942 Buna Campaign, New Guinea.
† Reestman, Milton Herman - SN O-675002, USAAF
823th Bomb. Sqdn., 38th Bomb. Gp., 5th AF; B-25 #42-64810 navigator; KIA 2 Feb 1944, Coral Sea off Port Moresby, New Guinea; plane lost on search & rescue mission; BNR.
† Rockwell, Harold Ralph - SN O-782622, USAAF, unit?, tail nbr.?
DNB 19 Feb 1945, Waa, New Guinea; plane crash.
† Shipman, Fred Howard, SN 17-178-496, USAAF, Harrison Co.
836th Engineering Aviation Bn.; KIA 19 May 1944 Wadke Is., W of Hollandia, Dutch New Guinea.
† Staub, Herman Edward - SN 37-074-568, US Army
Co. C, 163rd Inf. Regt., 41st Inf. Div.; KIA 15 Jan 1943 at Perimeter R, Soputa-Sanananda Track, New Guinea; died w/ Francis Tague; Buna Campaign.
† Tague, Francis Alvin - SN 37-084-585, US Army
Co. C, 163rd Inf. Regt., 41st Inf. Div.; KIA 15 Jan 1943 at Perimeter R, Soputa-Sanananda Track, New Guinea; died with Herman Staub; Buna Campaign.
† Wood, Charles Emmett Jr. - SN 17-041-753, US Army
Hq. & Hq. Co., 836 Engineering Aviation Bn.; KIA 30 Oct 1943 Lae, New Guinea; Operation Cartwheel.
† Wunder, Frank Grant Jr. - SN O-729400, USAAF
9th Fighter Sqdn., 49th Fighter Gp., 5th AF; P-38G Lightning #42-12856 pilot; KIA 13 Oct 1943 near Horanda, Papua, New Guinea; BNR.