 Like the Allies, the Japanese also relied on water transport to ferry supplies and reinforcements around the New Guinea, using a force of three submarines to avoid interdiction by Allied aircraft which had previously inflicted heavy casualties during the Battle of the Bismarck Sea.These submarines were augmented by barges, although they were limited in supply and were subject to attack by Allied aircraft and PT boats.Once the supplies had been landed, resupply parties were used to carry the stores overland on foot along a number of key tracks to their main troop concentrations around Sattelberg and Finschhafen.