Admiralty Islands Campaign - Background - Allied Plans

Allied Plans

In July 1942, the Joint Chiefs of Staff approved a series of operations against the Japanese bastion at Rabaul, which blocked any Allied advance along the northern coast of New Guinea towards the Philippines or northward towards the main Japanese naval base at Truk. In keeping with the overall Allied grand strategy of Europe first, the immediate aim of these operations was not the defeat of Japan but merely the reduction of the threat posed by Japanese aircraft and warships based at Rabaul to air and sea communications between the United States and Australia. By agreement among the Allied nations, in March 1942 the Pacific theatre was divided into the South West Pacific Area, under General Douglas MacArthur, and the Pacific Ocean Areas, under Admiral Chester W. Nimitz. Rabaul fell within MacArthur's area but the initial operations in the southern Solomon Islands came under Nimitz. The Japanese reaction was more violent than anticipated and some months passed before the Guadalcanal Campaign was brought to a successful conclusion. Meanwhile, General MacArthur's forces—primarily Australian—fought off a series of Japanese offensives in Papua in the Kokoda Track Campaign, Battle of Milne Bay, Battle of Buna-Gona, and the Battle of Wau.

At the Pacific Military Conference in March 1943, the Joint Chiefs of Staff approved the latest version of General MacArthur's Elkton plan for an advance on Rabaul. Owing to a shortage of resources, particularly heavy bomber aircraft, the final stage of the plan, the capture of Rabaul itself, was postponed until 1944. By July 1943, the Joint Chiefs were considering the possibility of neutralising and bypassing Rabaul, but the navy would still need a forward fleet base. The Admiralty Islands, already a part of the Elkton plan, could serve this purpose, as they contained flat areas for airstrips, space for military installations, and Seeadler Harbour, which was large enough to accommodate a naval task force. On 6 August 1943, the Joint Chiefs of Staff adopted a plan that called for the neutralisation rather than the capture of Rabaul, and scheduled the invasion of the Admiralty Islands for 1 June 1944.

Task Force Brewer Assault Echelon Units
Brigadier General William C. Chase

• 2nd Squadron, 5th Cavalry Regiment
• Battery B, 99th Field Artillery Battalion
• 673rd Anti-Aircraft Machine Gun Battery (Airborne)
• Reconnaissance Platoon, HQ Troop, 1st Cavalry Brigade
• Communications Platoon, HQ Troop, 1st Cavalry Brigade
• 1st Platoon, Troop B (Clearing), 1st Medical Squadron
• 30th Portable Surgical Hospital
• ANGAU Detachment
• Air Force Detachment
• Naval Gunfire Support Party
• Air Liaison Party

Throughout January 1944, AirSols aircraft based in the Solomon Islands and Royal Australian Air Force (RAAF) aircraft based on Kiriwina kept up a sustained air offensive against Rabaul. Under steady and relentless pressure, the Japanese air defence began to weaken, allowing a landing to be made on 15 February in the Green Islands, which lie little more than 100 miles (160 km) from Rabaul. On 16 and 17 February, the US Pacific Fleet's Task Force 58 attacked the main Japanese base at Truk. Most Japanese aircraft were recalled to defend Truk and 19 February saw the last significant interception of Allied aircraft over Rabaul. Meanwhile, on 13 February, General MacArthur had issued orders for the invasion of the Admiralty Islands, codenamed Operation Brewer, which was now scheduled for 1 April. Forces assigned included the 1st Cavalry Division; No. 73 Wing RAAF, providing close air support; the 592nd Engineer Boat and Shore Regiment (EBSR); the US Marines' 1st Amphibious Tractor Battalion; and US Naval Construction Battalions ("Seabees") to build the naval base—a total of 45,000 personnel. However, on 23 February 1944 three Fifth Air Force B-25 Mitchell bombers flew low over Los Negros. The airmen reported that there were no signs of enemy activity and the islands had been evacuated. Lieutenant General George Kenney, the commander of Allied Air Forces in the South West Pacific Area, went to MacArthur and proposed that the unoccupied islands be quickly taken by a small force. According to Kenney: "The General listened for a while, paced back and forth as I kept talking, nodded occasionally, then suddenly stopped and said: That will put the cork in the bottle."

Orders went out on 24 February 1944 for a reinforced squadron of the 1st Cavalry Division to carry out a reconnaissance in force in just five days time. If the Admiralty Islands were indeed evacuated, they would be occupied and a base developed. If the enemy was unexpectedly strong, then the force could be withdrawn. General MacArthur and Vice Admiral Thomas C. Kinkaid, the commander of Allied Naval Forces in the South West Pacific Area, would be on hand to make the decision but otherwise they delegated command to Rear Admiral William Fechteler, the commander of Amphibious Group 8 of Rear Admiral Daniel E. Barbey's VII Amphibious Force. To accommodate them, the light cruiser USS Phoenix was ordered to sea. At the time, she was in Brisbane, with over 300 of her crew on shore leave. Trucks with bull horns broadcast the code word recalling the crew. In order to achieve surprise, and to reach the Admiralty Islands in just five days, high speed transports (APDs) were required; Landing Ships, Tank (LSTs) were too slow to make the required distance in the time. Only three APDs were available: USS Brooks, Humphreys and Sands. Each could accommodate 170 men. The remaining troops were carried on nine destroyers: USS Bush, Drayton, Flusser, Mahan, Reid, Smith, Stevenson, Stockton and Welles. Between them, the destroyers and APDs carried 1,026 troops.

Task Force Brewer Supporting Echelon Units
Colonel Hugh Hoffman

• 5th Cavalry Regiment (less 2nd Squadron)
• 99th Field Artillery Battalion (less Battery B)
• 1st Platoon, Troop A, 8th Engineer Squadron
• 1st Collecting Troop, 1st Medical Squadron
• Signal Detachment, 1st Signal Troop
• 40th Naval Construction Battalion
• Battery C, 168th Anti-Aircraft Artillery Battalion (Gun)
• Battery A, 211th Coast Artillery Battalion (Anti-Aircraft) (Automatic Weapons)
• Company E, Shore Battalion, 592nd Engineer Boat and Shore Regiment

This force was commanded by Brigadier General William C. Chase, commander of the 1st Brigade, 1st Cavalry Division. It included the three rifle troops and the heavy weapons troop of the 2nd Squadron, 5th Cavalry; a platoon from Battery B, 99th Field Artillery Battalion with two 75 mm pack howitzers; the 673rd Anti-Aircraft Machine Gun Battery (Airborne); and 29 Australians of the Australian New Guinea Administrative Unit (ANGAU), who were to assist in gathering intelligence and dealing with the native population, some 13,000 of whom lived in the islands. Once the decision to remain was known, a follow-up force with the rest of the 5th Cavalry and 99th Field Artillery Battalion, 40th Naval Construction Battalion, and 2,500 measurement tons of stores would depart from Finschhafen in six Landing Ships, Tank (LSTs), each towing an LCM of Company E, 592nd EBSR. When an aide expressed concern over assigning such a hazardous mission to a unit without combat experience, General MacArthur recalled how the 5th Cavalry had fought alongside his father's troops in the campaign against Geronimo. "They'd fight then," he said, "and they'll fight now."

Major General Charles A. Willoughby's G-2 (intelligence) section did not agree with the airmen's assessment the islands were unoccupied. Drawing on Ultra and Allied Intelligence Bureau reports from interrogating local civilians, it reported on 15 February that there were 3,000 Japanese troops in the Admiralty Islands. On 24 February, it revised the estimate to 4,000. G-2 attributed the lack of anti-aircraft fire to the Japanese logistical situation, believing it was a measure to conserve ammunition. Lieutenant General Walter Krueger, the commander of U.S. Sixth Army later recalled no one at his headquarters believed the islands unoccupied. In the original plan, a team of Alamo Scouts was to have thoroughly reconnoitred the island before the landing. Krueger had a six-man party of Alamo Scouts inserted on the southern coast of Los Negros by PBY under cover of a bombing raid on 27 February. The scouts reported the south coast was "lousy with Japs".