Japanese intelligence about the Kokoda track, derived from pre-war espionage, was better than has been believed...
In 1931 the Japanese Ministry of Foreign Affairs embarked on a project to obtain intelligence on the 'southern area' - the region bounded in the north by the equator, west of Hawaii, east of India and as far south as Australia. Japanese consulates, including that in Australia, were instructed to gather information that would be of use should the Imperial Japanese Army and Navy extend their operations there. Spies were sent to accompany trade missions, even botanical expeditions were used to disguise espionage. At first New Guinea was not of major interest but by the late 1930s Japanese trading vessels, with Imperial Japanese Army and Navy officers on board, were charting the New Guinea coast and landing at ports.
One of these officers was Major Toyofuku Tetsuo of the Imperial Japanese Army. In March 1941, before the war against Japan commenced, he sailed into Port Moresby disguised as a member of the crew of the Takachiho Maru. Toyofuku wrote the Imperial Japanese Army's intelligence report on Papua, accompanied the Nankai Shitai there as its intelligence officer and was wounded at Isurava.
While ashore in Port Moresby Toyofuku purchased maps of Papua and walked around Port Moresby taking notes on and photographing locations of military importance. He had no opportunity to see the country north of Port Moresby and was curious to know if the road that headed in that direction allowed vehicles to drive to the other side of the Owen Stanley Range. He found that it did not and incorporated this information into his report.
It is one of the persistent myths of the Kokoda story that the Japanese believed that the Kokoda track was a vehicular road and statements to this effect can be found in the diaries of some Japanese soldiers. These men were not of sufficiently high rank to have access to Toyofuku's report and were simply repeating the gossip that is customary in military units when a new operation is about to begin. Toyofuku's report, completed seven months before the Japanese attack on Papua, contained an accurate list of the location and length of all roads in Papua at the time.
The report also contained intelligence on Papua gathered by the Japanese consulate in Sydney. Of particular importance were maps, made by Australian explorers, of the various tracks over the Owen Stanley Range. These maps and the information gained on Toyofuku's trip to Port Moresby were the key sources of intelligence used by Major General Horii Tomotaro in planning the July 1942 invasion of Papua.