Operation Cartwheel (1943 – 1944) was a majormilitary operation undertaken by theAllies in thePacific theatre ofWorld War II. The ultimate goal of Cartwheel was to neutralize the majorJapanese base atRabaul. The operation was directed by the Supreme Allied Commander in theSouth West Pacific Area (SWPA), GeneralDouglas MacArthur, whose forces had advanced along the northeast coast ofNew Guinea and occupied nearby islands. Allied forces from theSouth Pacific Area, under AdmiralWilliam Halsey, advanced through theSolomon Islands towardBougainville. The Allied forces from Australia, the Netherlands, New Zealand, theUnited States, and variousPacific Islands took part in the operation.^[1]

Japanese forces had captured Rabaul, on the island ofNew Britain in theTerritory of New Guinea, from Australian forces in February 1942. Rabaul became a majorforward base for Japanese forces in the South Pacific, and in turn became the main objective for Allied forces in the area. MacArthur formulated a strategy known as theElkton Plan to capture Rabaul, using bases in Australia andNew Guinea as staging points. Meanwhile, AdmiralErnest J. King, theChief of Naval Operations, proposed a plan with similar elements but under US Navy command.Army Chief of StaffGeorge C. Marshall, whose main goal was for the US to concentrate its efforts againstNazi Germany inEurope and not against the Japanese in the Pacific, proposed a compromise in which the drive towards Rabaul would be divided into three stages; the first under Navy command, and the latter two under MacArthur's direction and the control of the Army. This strategic plan, which was never formally adopted by the USJoint Chiefs of Staff but was ultimately implemented in practice, called for the following:

• CapturingTulagi (and later Guadalcanal) and theSanta Cruz Islands (Operation Watchtower)
• Capturing the northeastern coast of New Guinea and the central Solomons^[1]
• Reducing Rabaul and surrounding Japanese bases^[1]

The protractedbattle for Guadalcanal, followed by the unopposed seizure of theRussell Islands (Operation Cleanslate) on 21 February 1943, resulted in Japanese attempts to reinforce the area by sea. MacArthur's air forces countered in theBattle of the Bismarck Sea from 2–5 March 1943. The disastrous losses suffered by the Japanese prompted AdmiralIsoroku Yamamoto to initiateOperation I-Go, a protracted series of air attacks against Allied airfields and shipping at both Guadalcanal and New Guinea, during which Japanese naval air strength was significantlyattrited. Yamamoto waskilled on 18 April 1943 when his plane was shot down over the Solomon Islands.

On 12 February 1943 MacArthur presentedElkton III, his revised plan for seizing Rabaul before 1944. It called for the US Army forces under his command to advance on northeastern New Guinea and westernNew Britain, and forAdmiralWilliam F. Halsey Jr., commander of the South Pacific Area, to attack the central Solomon Islands. The plan required seven more divisions than were already in the theatre, which raised objections from the British. The US Joint Chiefs responded with a directive that approved the plan if forces already in the theatre oren route were used, and implementation of the plan was delayed by 60 days.Elkton III then becameOperation Cartwheel.

Cartwheel identified 13 proposed subordinate operations and set a timetable for their launching. Of the thirteen, Rabaul,Kavieng, andKolombangara were eventually dismissed as too costly or unnecessary; only 11 were actually undertaken (whereas theGreen Islands,^[2][3] only 117 miles from Rabaul, were substituted for Kavieng):

• Operation Chronicle – 30 June 1943
  • Woodlark Island (112th Cavalry Regiment)
  • Kiriwina (158th Regimental Combat TeamRCT US)
• Operation Toenails – 30 June 1943
  • New Georgia (43d Infantry Division US) – 30 June 1943
  • Segi Point, New Georgia (4th Marine Raider Battalion US) – 21 June 1943
  • Rendova (169th and 172nd RCT's US) – 30 June 1943
  • Zanana, New Georgia (169th and 172nd RCT's US) – 5 July 1943
  • Bairoko, New Georgia (4th Marine Raider Battalion US) – 5 July 1943
  • Arundel Island (172nd RCT, 43rd Infantry Division US) – 27 August 1943
• Vella Lavella (35th RCT,25th Infantry Division US,3rd Division New Zealand) – 15 August 1943
• Operation Postern – 5 September 1943
  • Lae, New Guinea (9th and7th Division Australia,503rd Parachute Infantry Regiment US)
• Operation Goodtime – 27 October 1943
  • Treasury Islands (8th Brigade New Zealand)
• Operation Blissful – 28 October 1943
  • Choiseul Island (2nd Marine Parachute Battalion US)
• Operation Cherryblossom – 1 November 1943
  • Bougainville (3d Marine Division US,37th Infantry Division US)
• Operation Dexterity
  • Arawe, New Britain (112th Cavalry US) – 15 December 1943
  • Cape Gloucester (1st Marine Division US) – 26 December 1943
  • Saidor (32nd Infantry Division US) – 2 January 1944
• Green Islands - 15 February 1944 (3rd Division New Zealand)
• Admiralty Islands – 29 February 1944 (1st Cavalry Division US)
• Emirau Island – 20 March 1944 (4th Marine Regiment US)

TheNew Guinea Force, under GeneralThomas Blamey, was tasked with thrusting eastward on mainland New Guinea. TheUS 6th Army, under GeneralWalter Krueger, was ordered to seize Kiriwina, Woodlark, andCape Gloucester. These land forces would be supported by Allied air units underLieutenant GeneralGeorge Kenney and naval units underVice AdmiralArthur S. Carpender.

In the midst of Operation Cartwheel, the Joint Chiefs met with PresidentFranklin Roosevelt and British Prime MinisterWinston Churchill at theQuadrant Conference inQuebec City in August 1943. There, the decision was made to bypass and isolate Rabaul rather than attempting to capture the base, now garrisoned by tens of thousands of Japanese troops. Soon afterward, the decision was made to bypass Kavieng as well. Although initially objected to by MacArthur, bypassing Rabaul instead of neutralizing it meant that his Elkton plan had been functionally achieved. After invading Saidor MacArthur moved on to his Reno Plan, an advance across the north coast of New Guinea toMindanao. This campaign, which stretched into 1944, showed the effectiveness of major Japanese force concentrations in favor of severing Japanese lines of supply and communication to more isolated island garrisons.

The Japanese Navy attempted to bolster Rabaul's defenses by requisitioning hundreds of carrier aircraft from Japanese carriers based atTruk in December 1943. This proved to be a costly strategic miscalculation, as Allied planes shot down between 200–300 Japanese carrier aircraft during raids on Rabaul, stripping Japan of irreplaceable veteran carrier pilots. Japan's highly selective pilot training program was unable to cope with the casualties incurred from mid-1942 until early 1944, including during Operation Cartwheel, and could not produce enough trained aircrew to replace mounting losses. The result was a gradual degradation of the IJN's existing naval aviation arm, a trend that contributed to the catastrophic Japanese naval defeat at theBattle of the Philippine Sea in June 1944.

The erosion of Japanese strength in the Solomons led directly to theAdmiralty Islands campaign, which was carried out in late February 1944, after the Allies had confirmed that the Japanese air threat from Rabaul had been effectively neutralized.

From February 1944 onwards, the Japanese declined to provision Rabaul with fighters or bombers for the rest of the war, mostly due to non-stop bombing of the base by land-based Allied airplanes only a few hundred miles away. The Japanese evacuated 120 aircraft to Truk on 19 February in an attempt to replace carrier aircraft destroyed defending Rabaul. The Japanese attempted to evacuate valuable by sea on 21 February, but their transport ship, theKokai Maru, was sunk by Allied bombers.^[4] The Japanese garrison at Rabaul became completely isolated, as their supplies dwindled and Allied domination of the seas and skies rendered reinforcement impossible. Some 70,000 Japanese troops remained trapped at Rabaul by the time Japan surrendered in August 1945.

• Structure of the Imperial Japanese forces in the South Seas Mandate, details on Japanese forces in bypassed islands

• Condon, John P. "Solomons Sunset-1944: Marine Aviation in the Reduction of Fortress Rabaul."Marine Corps Gazette 78.2 (1994): 66-73.
• Dunn, Richard L. "Shootout at Rabaul."Air Power History 59.3 (2012): 14-27.online
• Gamble, Bruce.Fortress Rabaul: The Battle for the Southwest Pacific, January 1942-April 1943 (Zenith Press, 2010)online.
• Nelson, Hank. "The troops, the town and the battle: Rabaul 1942."Journal of Pacific History 27.2 (1992): 198-216.

• The History Channel, June 30 — 1943 Operation Cartwheel is launched (2005)
• David Horner, "Strategy and Command in Australia’s New Guinea Campaigns" (2004)
• An Animated History of Operation Cartwheel (2006)Archived 3 March 2016 at theWayback Machine
• "Encyclopædia Britannica Article: The encirclement of Rabaul". Retrieved16 May 2006. Brief synopsis of Allied campaign to isolate Rabaul.
• "Rabaul and World War II". Archived from the original on 22 June 2004. Retrieved16 May 2006. Brief account of Japanese occupation of Rabaul and subsequent war crimes trials of many of the Japanese troops who had been stationed there.
• Mersky, Peter B. (1993)."Time of the Aces: Marine Pilots in the Solomons, 1942–1944".Marines in World War II Commemorative Series. History and Museums Division, Headquarters, US Marine Corps. Retrieved20 October 2006. Account of US Marine involvement in air war over Solomon Islands and Rabaul.
• "World War II Congressional Medal of Honor Recipient Major Gregory 'Pappy' Boyington". Archived fromthe original on 9 May 2006. Retrieved16 May 2006. Information on "Pappy" Boyington
• "Title: THE ASSAULT ON RABAUL. Operations by the Royal New Zealand Air Force December 1943 — May 1944". Retrieved30 May 2006.