Operation Cartwheel

Cartwheel Begins:
The Southwest Pacific

Invasion of Nassau Bay

by James Miller, jr.

Plans and Preparations

The invasion of Nassau Bay was designed to ease the problem of supplying the troops that were to attack Salamaua and Lae. They could not be wholly supplied by ship, by landing craft, by airplane, or by land. The threat of Japanese air attacks in the restricted waters of Huon Gulf and Vitiaz Strait, coupled with the prevailing shortage of troop and cargo ships, rendered the use of large ships impractical if not impossible.

The shortage of landing craft and the distance limited the extent of any shore-toshore operations. The Australian troops operating out of Wau against Salamaua were still being supplied by air, and this placed a heavy burden on Southwest Pacific air transport and limited the number of ground troops that could be employed.

In order to supplement air transport the Australians had begun their road from Edie Creek at the south end of the Bulolo Valley to the headwaters of the Lakekamu River on the southwest coast of the Papuan peninsula, but the tremendous difficulties inherent in pushing roads through New Guinea mountains slowed the Australians as they had the Japanese. It was clear that the opening of the Markham ValleyHuon Peninsula campaign would be delayed beyond August if it had to await completion of the mountain highway. (USSBS, Employment of Forces, pp. 21-22; ALF, Rpt on New Guinea Opns: Wau-Salamaua, 22 Jan13 Sep 43; Memo, Comdr ALF for GHQ SWPA, 5 May 43, sub: Warning Instns, in GHQ SWPA G-3 Jnl, 6 May 43.)

The seizure of Nassau Bay offered a possibility of at least partially solving these problems, a possibility which fitted neatly into the pattern of plans already being prepared. Nassau Bay lies less than sixty miles from Lae, or within range of the landing craft of the 2d Engineer Special Brigade which GHQ expected to employ, and it is just a short distance down the Papuan coast from Salamaua. Troops of the 3d Australian Division were operating inland from Nassau Bay at this time. Seizure of the bay by a shore-to-shore movement from Morobe, then held by the U.S. 162d Infantry of the 41st Division, would provide a means by which the Australians getting ready to attack Salamaua could be supplied by water to supplement the air drops, and would also provide a staging point for the shore-to-shore movement of an entire Australian division to a point cast of Lae. (GHQ SWPA 01 33, 7 May 43, in GFIQ SWPA G-3 Jnl, 8 May 43; Ltr, Land Hq [ALF] to Gen Off Commanding NGF, 17 May 43, sub: POSTERNSeizure Lae-Salamaua-Finschhafen-Madang Area, in GHQ SWPA G-3 Jnl, 7 Jun 43; GHQ SWPA 01 34, 13 Jun 43, in GHQ SWPA G-3 Jnl, 14 Jun 43.)

Therefore GHQ and New Guinea Force headquarters decided to seize Nassau Bay on the same day that Woodlark, Kiriwina, and New Georgia were invaded. The troops seizing Nassau Bay would then join forces with 3d Australian Division and press against Salamaua in order to keep the Japanese from deducing that the Allies were planning a major assault against Lae.

General Blamey was supposed to assume personal command of the New Guinea Force for the Markham Valley-Huon Peninsula operations but the pressure of his duties kept him in Australia until August. Pending his arrival in New Guinea Lt. Gen. E. F. Herring of the Australian Army retained command of the New Guinea Force and operated under Blarney's headquarters instead of GHQ as originally planned. Maj. Gen. Stanley G. Savige, General Officer Commanding the 3d Australian Division, had tactical command of the operations against Salamaua. Troops of the U.S. 162d Regimental Combat Team, which was assigned to Nassau Bay and subsequent operations against Salamaua, would come under General Savige's control once they were ashore.

When the Australians had defeated the Japanese attempt to capture Wau, they pursued the retreating enemy out of the Bulolo Valley and down through the mountains to a point inland from Nassau Bay. In preparation for Nassau Bay and the attack on Salamaua, Savige ordered his division to push against Salamatia from the west and south.

He directed the MacKechnie Force, essentially a battalion combat team of the 162d Infantry, to make the initial landing at Nassau Bay and operate on the right (cast) flank of his 17th Brigade.

At the same time the 24th Australian Infantry Battalion would create a diversion by operating against the Japanese detachments in the Markham Valley and establishing an ambush on the Huon Gulf at the mouth of the Buang River, halfway between Lae and Salamaua. (Map)

From 20 through 23 June the Japanese counterattacked the 17th Brigade's positions in the vicinity of Mubo and Lababia Ridge, a 3,000-foot eminence that is surrounded by the Bitoi and Buyawirn Rivers and has a commanding view of Nassau Bay to the southeast, Bitoi Ridge to the north, and the Komiatum Track which served as the line of communications from Salamaua to the Japanese facing the Australians.

The Japanese fought hard but failed to budge the 17th Brigade. Starting on 23 June they retired a short distance to the north. On 30 June Savige's 15th Brigade was attacking Bobdubi and the 17th Brigade, facing north, was holding Mubc, and Lababia Ridge. (ALF, Rpt on New Guinea Olms: Wau-Salamaua, 22 Jan-13 Sep 43; Incl 1, Tactical Sit to 1630, 30 Jun 43, to GFIQ SWPA G-2 Daily Summary of Enemy Int and G-2 Est of Enemy Sit 465, 30 Jun' Jul 43, in GHQ SWPA G-3 Jnl, 1 Jul 43.)

The MacKechnie Force, designated to land at Nassau Bay on 30 June, consisted of the reinforced 1st Battalion, 162d Infantry. In command was Col. Archibald R. MacKechnie, commander of the 162d. This regiment had arrived in New Guinea from Australia in February 1943Organized in March, the MacKechnie Force moved by land marches and seaborne movements in landing craft and trawlers from the Buna-Sanananda area to Morobe, where it set up defensive positions to protect an advanced PT boat base. For Nassau Bay the force was augmented by American and Australian units. (162d Inf Rpt of Opus, 29 Jun-12 Sep 43, in Morobe- Nassau-Bitoi Ridge-Mt. Tambu-Tambu Bay-Salamaua Area of New Guinea; William F. McCartney, The jungleers: A History of the 41st Infantry Division (Washington: Infantry journal Press, 1948), P. 51; Ltr, Col MacKechnie to Gen Smith, Chief of Mil HiSt, 20 Oct 53, no sub, OCMH.)

The augmented MacKechnie Force consisted of Lt. Col. Harold R. Taylor's ist Battalion, 162d; one platoon of the regimental Antitank Company; part of the regimental Service Company; one company of the 116th Engineer Battalion; elements of the 116th Medical Battalion and a portable surgical hospital; the 218th Field Artillery Battalion (75mm. pack howitzers), less A Battery; detachments from the 41st Division signal, quartermaster, and ordnance companies; detachments of the Combined Operational Service Command and the Australian New Guinea Administrative Unit, a military organization in charge of native affairs; a detachment of C Battery, 209th Coast Artillery Battalion (Antiaircraft); A Company, Papuan Infantry Battalion (native enlisted men and Australian officers); and A and D Companies of the 532d Engineer Boat and Shore Regiment, 2d Engineer Special Brigade.)

By late June the 3d Battalion, 162d, had relieved the MacKechnie Force of the mission of defending Morobe. Thirty days' supply and ten units of fire had been assembled. The troops trained for the landing by boarding PT boats, then transferring at sea to LCVP's, and debarking on beaches from the landing craft. On the night of 28 June the Intelligence and Reconnaissance Platoon, 162d, outposted the islands lying offshore between Nassau Bay and Mageri Point about ten miles north-northwest of Morobe, where the invasion was to be mounted, in order to install lights to guide the invasion flotilla. Colonel MacKechnie flew to the Bulolo Valley for a conference with General Savige, and at his request Savige dispatched one of his companies from Lababia Ridge to the mouth of the Bitoi River to divert Japanese attention from Nassau Bay.

As the landing was to be made in darkness, one platoon of this company was sent to the landing beach to set up lights to guide the landing craft. Company A, Papuan Infantry Battalion, of the MacKechnie Force, reconnoitered to Cape Dinga just south of Nassau Bay, and one of its scouts even sneaked into the enemy camp at Cape Dinga and spent the night with the Japanese. On the basis of the Papuan Infantry Battalion's reports it was estimated 300-400 Japanese were in the vicinity of Nassau Bay, and about 75 more near the south arm of the Bitoi River. (162d Inf Rpt of Opus; McCartney, The Jungleers, P. 52.)

The Enemy

This estimate was somewhat exaggerated. Present at Cape Dinga were about a hundred men of the 102d Infantry, 51st Division, and about fifty sailors of a naval guard unit. (This subsection is based on 8th Area Army Operations, Japanese Monogr No. 110 (OCMH), PP. 43-45; 18th Army Operations, II, Japanese Monogr NO. 42 (OCMH), 1-22; 18th Army Operations, Annex B (Maps), Japanese Monogr No. 47 (OCMH); Hist Div MIS CHQ FEC, Statements of Japanese Officials on World War II (English Translations), IV, 119-20, OCMH; Interrogation of Adachi et al. by Mil Hist Sec, Australian Army Hq, OCMH.)

The Japanese were expecting an Allied landing to come in Huon Gulf rather than at Nassau Bay, and had made their dispositions accordingly.

General Adachi, commanding the 18th Army from his headquarters at Madang, had been carrying out the 8th Area Army commander's orders to strengthen Wewak, Madang, Finschhafen, and especially Lae and Salamaua to protect Vitiaz Strait while preparing to attack Wau, Bena Bena, and Mount Hagen and infiltrate the Ramu and Sepik River Valleys. (See below, Map 12.)

The Madang-Lae Highway was still under construction but had been pushed only to the Finisterre Range which parallels the north coast of the Huon Peninsula. The Japanese correctly estimated that the Allies planned to use the air base sites in the mountain valleys to support their advances along the coast. Therefore they planned the moves against Wan and against Bena Bena and Mount Hagen, two outposts that had been used since 1942. The 6th Air Division, based in the Wewak area, was ordered to attack these points daily.

In command at Lae was Maj. Gen. Ryoichi Shoge, infantry group commander of the 41st Division. His command at this time was largely transient, as the 18th Army was sending troops through Lae to strengthen Salamaua. Since the March disaster in the Bismarck Sea, some troops had been landed at Lae from submarines, forty men per boat; others came in barges and destroyers to Cape Gloucester from Rabaul, thence to Finschhafen by barge and overland or by barge to Lae. In April and May the 66th Infantry (less the 3d Battalion), 51st Division, had been transferred to Salamaua from Lae, and elements of the 115th Infantry, the 14th Artillery Regiment, and the 51st Engineer Regiment, all of the 51st Division, staged through Lae for Salamaua. At Salamaua Lt. Gen. Hidemitsu Nakano, commander of the 51st Division, was directing operations.

The third infantry regiment of Nakano's division, the 102d, had made the January attack against Wan and had been almost continuously in action since that time.

By the end of June Nakano had six thousand men under his command. The Japanese defensive positions included the high ground inland from the shore--Mount Tambu, Komiatum, and Bobdubi.

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