page_title: Battle of Sio
section_title: Tactics and logistics
hierarchical_section_title: Battle of Sio / Prelude / Tactics and logistics
caption_attribution_description: English: Troop traffic between Kelanoa and Sio is by landing craft mechanized (LCM). This LCM has 80 men of the 30th Infantry Battalion and their equipment on board.
context_page_description: The Battle of Sio, fought between December 1943 and March 1944, was the break-out and pursuit phase of General Douglas MacArthur's Huon Peninsula campaign, part of the New Guinea campaign of World War II.
  After the defeat of the Japanese in the Battle of Sattelberg, Australian Army forces broke through the Japanese positions around Finschhafen. Constant pressure from US Navy PT boats, Australian land forces and Allied aircraft brought the Japanese logistical system to the brink of collapse, resulting in disease, malnutrition, and privation for the Japanese soldiers. Meanwhile, the Allied supply system grappled with the problems of terrain and climate, particularly inclement weather and rough monsoonal seas that hampered and occasionally prevented delivery of supplies by sea.
  Australian and Papuan troops advanced along the coast of the Huon Peninsula, using infantry, tanks, and air strikes against the Japanese positions, which were generally sited at creek crossings in the jungle. The advancing infantry kept strictly within range of the supporting artillery, which was liberally employed in the early stages of the operation.
context_section_description: The main Australian advance was by infantry-tank-engineer teams moving along the coastal tracks. Japanese positions were generally sited at creek crossings in the jungle. The advancing infantry kept strictly within range of the supporting artillery, except for short periods during the latter stages of the operation when Japanese opposition was negligible and the difficulty of moving the artillery forward quickly was too great. A secondary outflanking movement was made inland, over the higher ground, which was usually coral cliffs covered by kunai grass and rising as high as 4,000 feet (1,200 m). Since the Japanese intent was to delay rather than fight to the death, a threat to their escape route usually prompted a withdrawal. When this did not occur, the position was reduced by a combination of manoeuvre and tank, mortar, and artillery fire. During the early part of the advance, 4,700 rounds were fired in one day; but during the entire 5th Division advance from Sio to Saidor, only 30 rounds were fired. The advance was made in a series of bounds, the objective of which was usually to secure sheltered beachheads.
  Allied supply was entirely by sea. Amphibian scouts from the US 532nd Engineer Boat and Shore Regiment (EBSR) of the US 2nd Engineer Special Brigade, wearing Australian uniforms, advanced with the infantry and reconnoitred beaches from the landward side as they were secured. If a beach looked suitable, a second reconnaissance was made from the sea. Once a beach was selected, a shore party was brought in by landing craft to set up an administrative area. Engineers improved the coastal track to enable supplies to units moving along it to be brought up by jeeps but supplies for units moving inland over the high ground had to be brought by native carriers. Artillery guns were brought forward over the tracks or else were moved by Landing Craft Mechanised (LCMs) of the 532nd EBSR. Tanks normally moved along the tracks but used LCMs to bypass obstacles. As the advance continued, new beachheads were opened up while rearward ones were closed. The advance was halted on occasion to allow for the guns to be brought forward or sufficient supplies to be accumulated at the forward beachhead.
  The major problem was the weather. The monsoon caused rough seas that precluded the use of the small Landing Craft, Vehicle, Personnel (LCVPs) and restricted the operations of the larger LCMs. Because of the extremely rough seas—the most difficult that the 532nd EBSR had ever encountered—most supply missions were by night when tidal conditions were most favourable. Wootten insisted that at least seven days' supplies be available in forward areas in case the weather prevented the LCMs from running. II Corps made available two trawlers, manned by the 1st Water Transport Group, to deliver rations. The Australian Army also moved supplies by DUKWs.
caption: An LCM of the 532nd EBSR ferries men of the 30th Infantry Battalion from Kelanoa to Sio
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