This was the US definitive version of ‘Princeton’, the outline plan for the recapture of the Visayan and Mindanao islands in the Philippine islands group, Borneo, and the Netherlands East Indies (April 1945).
The ‘Montclair’ plan was finally but only partially executed in the Australian ‘Oboe’ operations against Borneo and the US ‘Victor’ operations in the Philippine islands group.
In preparation for anticipated operations against the Japanese home islands, the USA on 5 April 1945 reorganised its command structure in the Pacific theatre, the previous South-West Pacific Area (except the Philippine islands and Hainan island) being shifted from the command of General Douglas MacArthur, as being a distraction to his strategic objectives, to that of Admiral the Lord Louis Mountbatten’s South-East Asia Command (Borneo, Java and Celebes islands) and to Australia (portions of the previous South-West Pacific Area to the east of Celebes island), though portions of the latter to the west of the Australian Mandated Territories were during August transferred to SEAC on the request of the Australian administration.
‘Montclair’ was planned by the original South-West Pacific Area command under MacArthur, and was thus undertaken as a joint US and Australian effort, with the portion concerned with the Visayan islands group falling to Lieutenant General Robert L. Eichelberger’s US 8th Army and the portion concerned with Borneo to Lieutenant General Sir Leslie Morshead’s Australian I Corps. The latter became available as a formation for mobile operations after the establishment in September 1944 of Lieutenant General Vernon A. H. Sturdee’s Australian 1st Army to replace the miscellany of Australian formations which had been engaged in the blockade of Japanese forces isolated in New Guinea, while the 8th Army undertook a comparable task in the island groups to the north of New Guinea.
Although the US plans called for the Japanese garrisons in all of the Philippine islands other than Leyte and Luzon to be eliminated by Filipino guerrillas in association with a re-formed Filipino army, MacArthur pre-empted them and on 6 February ordered Eichelberger to mop up Japanese forces in the central and southern parts of the Philippine islands group with his 8th Army supported by the amphibious capabilities of Vice Admiral Thomas C. Kinkaid’s 7th Fleet, and at the same time decided that the I Corps should retake Borneo to provide the US forces for the invasion of Japan with adequate supplies of oil.
Once Borneo had been seized, in MacArthur’s plan the I Corps was to proceed to the invasion of Java. The US Joint Chiefs-of-Staff accepted MacArthur’s fait accompli on 3 April, just before MacArthur and Admiral Chester W. Nimitz were appointed to command all the land and naval forces respectively in the Pacific Theater. The operations planned by Eichelberger were in fact a series of overlapping joint undertakings.
In the first of these, Eichelberger’s 8th Army was to take Palawan island in ‘Victor III’, the western tip of Mindanao island plus Basilan and Jolo in the Sulu islands group in ‘Victor IV’ to secure the entrances to the Sulu Sea and to establish airfields from which operations in Borneo could be provided with tactical air support.
In the second, the 8th Army was to take the Visayan islands group (Panay, Cebu, Negros and Bohol) in ‘Victor I’ and ‘Victor II’, and in the third the US forces were to clear Mindanao island in ‘Victor V’.
The Japanese forces faced by the men of Eichelberger’s command were the 102,000 or so troops of Lieutenant General Sosaku Suzuki’s 35th Army, of which about 43,000 were located on Mindanao island and the other 59,000 scattered over scores of islands large and small. The headquarters of the 35th Army was located on Cebu in the Visayan islands group, and Eichelberger was under no misapprehension about the difficulty of the task entrusted to his army, which by the middle of April 1945 had launched 38 large and many smaller amphibious landings.
As a preliminary to these far-flung operations, Eichelberger first cleared the maritime route through the Visayan Passages to remove the considerable detour US shipping had been forced to make to avoid these Japanese-held approaches to Manila.
At this time the 8th Army held Leyte island and a relatively small beach-head on Samar island over the San Juanico Strait from Leyte, and Eichelberger thus launched his forces in a series of small operations to take the northern shore of Samar and so open the San Bernardino Strait between Samar and Luzon islands (Major General William H. Arnold’s Americal Division, landed from Leyte on 19 February), followed by operations to take smaller islands such as Burias (the Americal Division, landed from Leyte on 8 March), Siniara, Romblon and Tablas (part of Major General Roscoe B. Woodruff’s 24th Division, landed from San Jose on Mindoro on 11/12 March), and Masbate (part of Major General Rapp Brush’s 40th Division, landed from Leyte on 3 April).
Eichelberger’s forces had cleared the Visayan Passages by 5 April, and could now be devoted to the recapture of the central and southern parts of the Philippine islands group, whose liberation had already begun with the landing of the 186th Regimental Combat Team of Major General Jens A. Doe’s 41st Division, supported by the 6th Amphibious Group, at Puerto Princesa on central part of Palawan island on 28 February. Palawan and its offshore islands were garrisoned by some 2,900 Japanese. By 2 March the surviving Japanese had taken to the mountains, and by 22 April the Palawan group had been secured for minimal US casualties, other landings having taken the islands of Dumaran (9 March), Busuanga (9 April), Balabac (16 April) and Pandaman (22 April). The all-weather airfield was in US service by 20 March, allowing tactical air attacks against Japanese targets in Borneo and the southern part of the Philippine islands group to start almost immediately, strategic attacks on targets in China following from April.
Next on Eichelberger’s list was the western tip of Mindanao island, where the rest of the 41st Division landed around Zamboanga on 10 March, and in two weeks of heavy fighting took the town and its airfield, forcing the local garrison, Major General Takichi Hojo’s 54th Independent Mixed Brigade, to seek refuge in the mountains of the peninsula, where it was harried by Filipino guerrillas for the rest of the war.
The 41st Division now turned to the south-west and the Sulu archipelago stretching out to Borneo. Basilan island was taken against limited opposition on 10 March, and then the 163rd Regimental Combat Team was sent to the far south where it took the Tawi-Tawi islands group on 2 April before falling on Jolo island in the centre of the archipelago on 9 April. Again a successful landing was made, but the 4,000 Japanese of the garrison fought stoutly for three weeks until pulling back to the middle of the island, where they held out until the end of June.
The Visayan islands group was the 8th Army’s next objective, and here two formations (the 40th and Americal Divisions) were used, the former on Panay island and Negros Occidental (the portion of Negros island to the west of the central mountain chain), and the latter on Negros Oriental, Cebu island and Bohol isloand. Part of the 40th Division, supported by the 9th Amphibious Group, landed to the west of Iloilo on Panay island on 18 March, and with Filipino guerrilla aid closed on the 2,750-man garrison holding a position in front of Iloilo. The Japanese fired the town and fell back into the mountains, surviving until the end of the war in limited numbers.
The division was then shipped over to Negros Occidental, landing to the south of Bacolod on 29 March. The island was garrisoned by 13,000 Japanese under Major General Takeishi Kono, commanding the 77th Brigade, and the first of these were encountered as the 40th Division probed to the north toward Bacolod on 5 April. By 4 June the back of the Japanese defence had been broken and its survivors followed the standard practice of retiring into the mountains where they were hunted by Filipino guerrillas to the end of the war, when a remnant of 6,000 men surrendered.
The most severe battle of the campaign was that for Cebu island in 'Victor II'. Here Suzuki had some 13,500 Japanese troops to oppose the Americal Division when the Americans landed near Cebu City on 26 March. Fighting its way through well-sited minefields, the division took Cebu City on the following day and pursued the Japanese to the north as they fell back to prepared positions. Suzuki’s forces were driven out of these on 18 April and then took to the mountains, where parties survived until the end of the war; on 10 April Suzuki and his staff tried to escape to Mindanao in small boats, but were spotted and attacked by aircraft on 19 April. Suzuki was killed, and succeeded in command of the 35th Army by Lieutenant General Gyosaku Moruzumi, the commander on Mindanao island.
The last of the Visayan islands group to receive the 8th Army’s attention was Bohol as the last element of 'Victor II'. Here the reserve regiment of the Americal Division landed on 11 April and overcame limited resistance by 20 April. The regiment was then landed on Negros Oriental during 26 April to supplement the efforts of the 40th Division in reducing the island by 12 June.
For the loss of 835 dead and 2,300 wounded, the Americans had taken the Visayan islands group against substantial numbers of Japanese, who lost at least 10,000 dead and 500 prisoners to the Americans, and then large numbers to the Filipino guerrillas in the mountains before some 17,500 survivors surrendered at the end of the war.
The only Japanese-held island of importance in the Philippine islands group was now Mindanao, held by the 35th Army with the 43,000 men of Lieutenant General Jiro Harada’s 100th Division and the 32nd Naval Base Force at Davao toward the south of the island, the 74th Regiment at Malaybay in the centre of the island, and half of Lieutenant General Gyosaku Morozumi’s 30th Division at Cagayan on the north coast. However, the Japanese were generally confined to the towns and main roads by Colonel Wendell W. Fertig’s 25,000 Filipino guerrillas, who controlled some 90% of the island.
The Japanese defence plans were still posited on an American attack from the south, so in 'Victor V' the 8th Amphibious Group put Major General F. C. Sibert’s X Corps (24th Division from Mindoro and Major General Clarence A. Martin’s 31st Division from Morotai) ashore on 17 April at Parang and Malabang in Illana Bay, on the west of the island. The 24th Division pushed up the line of the Mindanao river and reached Digos on Davao Gulf during 27 April, then turned to the north to take Davao on 3 May as the Japanese pulled back along the road to Malaybay. The 24th Division drove the Japanese back up the Malaybay road only on 10 June. Meanwhile the 31st Division was pushing along the north-western side of the island toward Cagayan, but was checked short of its objective on 5 May. The way was then opened by a landing in the Japanese rear (in Macajalar Bay to the east of Cagayan) by the 108th Regimental Combat Team during 10 May. The Japanese were now pushed back into the heart of the island.
Four more US landings were made between 1 June and 12 July in the south of the island, and the Japanese were firmly contained to sit out the war in two pockets, one of 20,500 men in the centre of the island and another of 2,000 men in the south.
The campaign for the Philippine islands group had ended, therefore, where MacArthur first planned to start it, on Mindanao.
During this period the I Corps was also reconquering the most important portions of the island of Borneo held by Lieutenant General Masao Baba’s 37th Army, with headquarters at Jesselton, 10 battalions in Brunei and northern Borneo, one and a half battalions in Kuching, one and a half battalions in Bandjermasin, one battalion and naval troops at Balikpapan, one battalion and naval troops in Tarakan, and one battalion at Miri.
The I Corps began to group on Morotai island on 22 February 1945 with Major General Edward J. Milford’s Australian 7th Division and Major General George F. Wootten’s Australian 9th Division as its principal formations. The first move was ‘Oboe I’ to seize Tarakan island from 1 May using 13,000 men of Brigadier David Whitehead’s 26th Brigade Group of the 9th Division, supported by the US 6th Amphibious Group and with 5,000 men of the Royal Australian Air Force under command.
The Japanese resistance was great, although found by only 2,000 men, and the island was not declared secure until 24 June, by which time the Australians had lost 225 dead and 669 wounded. The Japanese losses were 1,540 dead and 252 taken prisoner, and 300 men held out until the end of the war.
Next came Brunei Bay, the target for the 9th Division (less its 26th Brigade Group) against Major General Taijirou Akashi’s 56th Independent Mixed Brigade (the 371st Independent Battalion at Labuan, and the 366th and 367th Independent Battalions at Brunei). This ‘Oboe VI’ operation lasted from 10 June to 1 July, by which date the Australian 20th and 24th Brigades had lost 114 dead and 221 wounded, compared with 1,234 Japanese dead and 130 taken prisoner.
The capture of Balikpapan in ‘Oboe II’ was allotted to the 7th Division supported by the US 8th Amphibious Group, and air and naval support was furnished by Australian, Dutch and US forces. A full strength of 33,500 (including corps troops and attached air units) was brought to bear on excellent fixed defences and a garrison of 4,000 Japanese of the 454th Independent Battalion and 22nd Base Force. The landing began on 1 July after an intense air and naval bombardment, and by 9 July the Australians had taken the port and its two airfields. By the end of the month the surviving Japanese had fled into the interior of Borneo, leaving 1,783 dead and 63 prisoners to the Australians, who had secured their objectives at the cost of 229 dead and 634 wounded, and by the time hostilities ended in the middle of August the Australians had cleared the area within some 15 to 20 miles (24 to 32 km) of the port.
The I Corps had taken all three of its objectives in Borneo during the ‘Oboe’ operations, adding a useful local fuel supply to the Allied effort in the Pacific. The Balikpapan operation was the last major amphibious operation of World War II, and the largest amphibious operation undertaken by the Australians.