Operation Cartwheel

Markham Valley and the Huon Peninsula

Strategic Reconsiderations

by James Miller, jr.

The Japanese Pull Back

The fall of Lae and Salamaua, coming hard on the heels of defeat in the central Solomons, had a profound effect upon Japanese strategic plans, an effect that went far beyond the immediate importance of Lae and Salamaua. Although the twin losses of Guadalcanal and Buna were severe, Imperial General Headquarters had not regarded these as irretrievable. It had continued to prepare plans for offensives in the Southeast Area. (This subsection is based upon: 8th Area Army Operations, Japanese Monogr No.110 (OCMH), pp. 80-87; and 18th Army Operations, II, Japanese Monogr No. 42 (OCMH), 19-22, 48-53, 58-64, 8486, 151-54.)

Now the war leaders in Tokyo reassessed the situation and determined on a drastic retrenchment.

The fall of the central Solomons and of Lae-Salamaua closely followed the loss of Attu and the evacuation of Kiska in the Aleutians, and came at a time when Imperial Headquarters entertained well-justified fears about the opening of an Allied offensive through the Central Pacific. (The offensive began in November 1943. See Philip A. Crowl and Edmund G. Love, The Seizure of the Gilberts and Marshalls, UNITED STATES ARMY IN WORLD WAR II (Washington, 1955).)

The Japanese in September decided that they were overextended. They determined to withdraw their perimeter in order to set up a defense line that would hold back the Allies while they themselves marshaled their strength for decisive battle. This perimeter would be strongly manned and fortified. It was hoped that the defensive preparations behind it would be completed by the early part of 1944.

So Imperial Headquarters drew its main perimeter line from western New Guinea through the Carolines to the Marianas. This was "the absolute national defense line to be held by all means. (118th Area Army Operations, Japanese Monogr No. 110 (OCMH), p. 87.)

The Southeast Area, including Rabaul, once the focus of such great but elusive hopes for victory, was now on the outpost line.

But the war was far from over for MacArthur's and Halsey's troops. General Imamura. and Admiral Kusaka were no longer counted on to win decisively, but they were ordered to hold out as long as possible, and so delay the Allied advance. To strengthen the Southeast Area, Imperial Headquarters in September ordered the 17th Division from Shanghai to Rabaul "to reinforce the troops manning the forward wall." (Japanese Operations in the Southwest Pacific Area (Vol. II of MacArthur hist), Ch. VII, P. 26, OCMH.)

Imamura and Kusaka determined to hold Bougainville, whose defenses they had been trying to build up during the long fight on New Georgia, to develop and strengthen Madang and Wewak, to develop the transport system connecting the main bases of the Southeast Area, and to hold Dampier and Vitiaz Straits. Control of these straits had been essential to nearly all Japanese movements to New Guinea and, as before, the Japanese were resolved to hold them in order to block any Allied westward advance. (see Map 12)

To this end Imamura, who kept the 38th Division under his control to defend Rabaul, had previously dispatched the reinforced 65th Brigade to Tuluvu on the north coast of Cape Gloucester with orders to develop a shipping point there and to maintain the airfield. On 5 September he sent Maj. Gen. Iwao Matsuda to Tuluvu to take command of the 65th Brigade, some elements of the 51st Division, and the 4th Shipping Group. To Matsuda's responsibility for handling shipping he added that of defending the coasts of western New Britain.

On the New Guinea side of the straits, the Japanese regarded Finschhafen as the key defensive position. Possessed of two good harbors-Finschhafen itself and Langemak Bay- and a small airfield, it had long been used as a barge staging point.

In early August Adachi had been concerned about a possible attack against Finschhafen, but he did not have enough troops to strengthen its small garrison substantially while the 41st Division was defending Wewak, the 51st Division was defending the Lae- Salamaua area, and the 20th Division was working on the Madang-Lae road. He did, however, send the 80th Infantry and one battalion of the 21st Field Artillery Regiment of the 20th Division from Madang to Finschhafen. By the end of August Maj. Gen. Eizo Yamada, commanding the 1st Shipping Group and the combat troops at Finschhafen, had about one thousand men.

When the 9th Australian Division landed east of Lae on 5 September, Adachi foresaw the danger. to Finschhafen. He suspended construction of the Madang-Lae road, which was now a twenty-foot-wide all-weather road running along the coast from Madang to Bogadjim, thence over the Finisterre Range at a defile named Kankirei and into the Ramu Valley to a point ten miles north of Dumpu. This decision freed the 20th Division for combat duty. Adachi ordered a small force of the 20th Division, under Maj. Gen. Masutaro Nakai, the divisional infantry commander, to advance to Kaiapit, which is on the uplands near the sources of the Markham and Ramu Rivers. The move was intended to keep the Allies from advancing through the Ramu Valley, over Kankirei to the coast, and on against Madang and Wewak, and was also to help cover the retreat of the 51st Division from Lae up the trough to Madang. When Adachi decided not to use the Markham and Ramu Valleys for the retreat he ordered Nakai north to hold the Kankirei defile.

Adachi ordered the main body of the 2oth Division, commanded by Lt. Gen. Shigeru. Kitagiri, to march to Finschhafen. The division departed Bogadjim on io September on its march of nearly two hundred miles, but was still far from its destination when the Allies struck the next blow.

Allied Decisions

General MacArthur's ELKTON III called for the capture of Finschhafen as a step toward gaining control of Vitiaz and Dampier Straits. The plan had set the tentative date for the move against Finschhafen at six weeks after the invasion of Lae. At least two factors, however, impelled a speed-up in the timetable. The first was the quick fall of Lae and Salamaua after the landing on 4 September. The second was the 20th Division's move toward Finschhafen. But before orders could be sent out for the capture of Finschhafen, it was necessary to consider this operation in relation to the larger problems involved in capturing Madang, an operation considered necessary to protect the left flank during the seizure of Cape Gloucester. Seizure of Finschhafen, Madang, and Cape Gloucester would of course give physical control of both sides of the straits to the Allies. ( See above pp. 27, 19o and Chart 2. This subsection is based on ALF, Rpt on New Guinea Opns: 4 Sep 43-26 Apr 44; Ltr, Blamey to MacArthur, 31 Aug 43, no sub, in GHQ SWPA G-3 Jnl, 31 Aug 43; Memo, Chamberlin for CofS GHQ SWPA, 3 Sep 43, sub: Comment on Ltr From Cmdr ALF, P Aug 43, Opns for Capture of Madang, same file; Chamberlin's Memo for File, 3 Sep 43, same file; and GHQ SWPA 01 34/12, 15 Sep 43, in GHQ SWPA G-3 Jul, 14 Jul 43; GHQ SWPA 01 34/14, 17 Sep 43, same file.)

Capture of Madang was bound to be a large operation. Allied intelligence estimated that in late August a total of 55,000 Japanese held the regions between Lae and Wewak. At this time General Blamey, in a letter to MacArthur, held that the Japanese would exert every effort to defend the Markham and Ramu Valleys, Bogadjim (near the defile into the Ramu), Lae, Salamaua, and Finschhafen. Capture of Madang, which had been assigned to his New Guinea Force, would require as preliminary conditions complete air and naval superiority, support by the VII Amphibious Force, physical possession of Lae, the Markham Valley, Salamaua, and Finschhafen, and the neutralization of the Japanese in western New Britain.

Blamey set forth three steps to be followed after the capture of Lae. The first was the capture of Finschhafen by a seaborne assault. Blarney recommended as the second step seizure of an intermediate objective between Finschhafen and Bogadjim, because 256 miles of water separated Lae from Bogadjim, 178 separated Finschhafen and Bogadjim, and these were long distances to travel with a flank exposed. The third and final step would be the capture of Madang by a combination of airborne invasion and amphibious assault coupled with pressure from troops advancing northwestward out of the Ramu Valley. To avoid exposing the right flank, he strongly urged capturing Cape Gloucester (which had been assigned to the ALAMO Force) before taking Madang. This would be feasible, he argued, because Madang was so much farther from Finschhafen than was Cape Gloucester.

These proposals received close study at the advanced echelon of GHQ, which had moved to Port Moresby during the planning for Lae and the Markham Valley. General Chamberlin looked on them as generally sound. Regarding Blamey's concern over control of Cape Gloucester as well as the coasts of the Huon Peninsula, however, he pointed out to General Sutherland that "G-3 believes that a physical occupation of areas has little bearing on the control of Vitiaz Strait but considers that airfields strategically placed which cover the water areas north of Vitiaz Strait are the controlling considerations." (Memo, Chamberlin for CofS GHQ SWPA, 3 Sep 43, sub: Comment on Ltr From Comdr ALF, 31 Aug 43, Opus for Capture of Madang, in GHQ SWPA G-3 Jnl, P Aug 43. Japanese sources often use "Dampier Strait" to mean both Vitiaz and Dampier Straits; Allied sources often use "Vitiaz Strait" for both.)

As to the intermediate objective between Finschhafen and Bogadjim, which Chamberlin placed at Saidor (with a harbor and prewar airfield) on the north coast of the Huon Peninsula, he felt that little would be gained by seizing it as well as Madang. On the other hand it appeared that Saidor might prove a satisfactory substitute for Madang.

Timing of operations would be tricky, largely because the VII Amphibious Force lacked enough ships to conduct two operations at once. It would be committed to operations on the Huon Peninsula until mid-November.

Therefore the Cape Gloucester invasion could not take place until about 1 December, but the attack against the north coast of the Huon Peninsula would also have to be launched about the same time if the New Britain offensive was to be protected effectively. For these reasons Chamberlin recommended deferring the decision on whether to move to New Britain before or after invading the north coast of the Huon Peninsula. For this latter operation, he proposed two alternatives: seizure of a prewar airfield at Dumpu in the Ramu Valley without operating on the coast at all, or seizure of the Saidor airfield without operating in the Ramu Valley.

The questions were threshed out at a conference at Port Moresby on 3 September. MacArthur, Sutherland, Chamberlin, Kenney, Whitehead, Blarney, Carpender, and others attended. Blarney spoke strongly in favor of his recommendations. Kenney urged a deep penetration of the Ramu Valley all the way to Hansa Bay, which lies between Madang and Wewak. After Hansa Bay, he recommended, the advance could turn southward in co-ordination with the Cape Gloucester attack. Admiral Carpender wanted an operation somewhere between Madang and Saidor to precede Cape Gloucester. He received some support in his view from MacArthur, who asserted the necessity for seizing an area between Finschhafen and Madang before capturing Cape Gloucester, so as to assure the safe movement of supplies to support the latter operation.

After a good deal of discussion, opinion crystallized in favor of covering the move to Gloucester by seizing the line DumpuSaidor. Dumpu would be seized at once by airborne and overland advances, and would then be used to cover simultaneous moves against Saidor and Gloucester. These moves, Chamberlin estimated on 3 September, would take place about 1 November at the earliest, but 1 December was more probable.

Thus it was that on 15 September MacArthur ordered Blarney's New Guinea Force, supported by Kenney's forces, to seize Kaiapit at the head of the Markham Valley and Dumpu about thirty miles south of Bogadjim. Two days later he ordered the New Guinea Force, with naval support, to capture Finschhafen. It would serve as an advanced air base, and Allied Naval Forces, basing light naval craft there, would use it to cut off the Japanese from Cape Gloucester and Saidor. The attack on Madang was postponed.

Advance Through the Ramu Valley

With his forces converging on Lae from east and west General Blarney completed plans for Kalapit and Dumpu. Tactically the initial phases of the task appeared fairly simple; patrols had reported the area between Nadzab and the Leron River, a tributary of the Markham, to be free of the enemy. (This section is based on ALF, Rpt on New Guinea Opus: 4 Sep 43-26 Apr 44; Craven and Cate, The Pacific: Guadalcanal to Saipan, pp. 190-93.)

Logistics would present the greatest difficulty. No overland line of communications existed, and until roads were built all supplies for the advancing troops would have to be flown in. This fact limited the attacking force to one division (the 7th) of but two brigade groups.

The 2/6th Australian Independent Company began the drive in September when Kenney's transport planes landed it on a prewar airstrip in the Markham Valley some thirty miles northwest of Nadzab near the Leron River. The 2/6th then made its way eight miles up the river to Kaiapit, after a sharp encounter on 19 September, captured the village from a small group of Japanese, and held it against their repeated counterattacks. Two days later the Kaiapit strip saw the arrival, after a flight up from Nadzab, of the 21st and 25th Brigade Groups of General Vasey's 7th Australian Division.

At the month's end the 21st Brigade, followed by the 25th, left Kaiapit and entered the Ramu Valley. By 6 October the 2ist was in possession of Dumpu, where 7th Division headquarters was established. The great Markham-Ramu trough had fallen with an ease that the Allies had not expected, an ease brought about by the hasty Japanese decision not to retreat through the trough.

Behind the lines engineers set to work building a truck highway from Lae to Nadzab along the prewar road, but rain fell during forty-six of the final sixty days of the project and it was December before the task was finally finished and large amounts of supplies could be sent to Nadzab. Nadzab and the other sites in the Markham and Ramu Valleys received all their supplies and equipment by airlift during the period the road was under construction.

By the end of December Allied Air Forces possessed three first-class air bases in full-scale operation in the Markham and Ramu Valleys: one at Nadzab, one at Lae, and one at the juncture of the Gusap and Ramu Rivers. The last site was selected in preference to Kaiapit, which proved too swampy and malarious for extensive development. Dumpu served as a staging field for fighter planes.

After establishing strong positions at Dumpu, the 7th Australian Division continued its part in seizing the Huon Peninsula. Marching north-northwest from Dumpu, it attacked Nakai's positions in the defiles of the Finisterres. The defiles were secured in February after almost three months of the most arduous kind of fighting. Nakai retreated toward Madang while Vasey's division broke out to the coast east of Madang.

More Markham Valley and the Huon Peninsula

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