If the Australian knowledge of the strength and disposition of Japanese forces on Bougainville was poor, the Japanese knowledge of the Australians was woeful. The Japanese Seventeenth Army's military intelligence section was pitifully small, consisting of only four officers: a lieutenant-colonel, two captains, a lieutenant and ten soldiers. Their duties consisted of compiling information on the enemy, preparing maps, issuing meteorological information and controlling the Kenpei-tai. The Kenpei carried out the role of military police and controlled interactions with the Bougainvilleans. From atop the Numa Numa trail, the Japanese could see the troopships anchored in Torokina harbour and watch the Australians arrive and the Americans depart. In November 1944 a Bougainvillean from Torokina told the Japanese that Australian troops were in the perimeter. This was confirmed the following month when the Japanese heard a radio broadcast by MacArthur announcing that Australian soldiers had relieved the Americans. The Japanese knew little else about the Australian force.

When senior Japanese officers were questioned at the end of the war, Lieutenant-Colonel Miyakawa Kiyoshi, a Seventeenth Army intelligence officer, and Lieutenant-Colonel Kanda Hachio, a 6th Division staff officer, said that there had been no attempt to compile an order of battle of Australian units or to identify any of the Australian commanders. All they knew was that the Australians comprised units from the 3rd and 11th Divisions, and they had been able to identify the 24th and 25th Battalions. The senior Japanese commanders were only interested in the number of troops and not unit designations or personalities. Miyakawa thought there were between 50000 and 60000 Australians on the island. It was one of those curiosities of war that Japanese intelligence doubled the number of Australians while Australian intelligence halved the number of Japanese.