Australia–Japan Research Project at the Australian War Memorial
The human face of war
HORII supply proposal

In mid-June 1942, during the early planning phase for the overland operation to capture Port Moresby, the commander of the South Seas Force, Major General HORII Tomitarô, and his Chief of Staff, Lieutenant Colonel TANAKA Toyonari, met with staff of the 17th Army Headquarters at Davao in the Philippines to discuss the operation. HORII was unenthusiastic about the prospects of the success of the mission, and reportedly gave the following assessment to his superiors.

The South Seas Force will identify the best route from Buna through Kokoda to Port Moresby. From Buna to Kokoda is approximately 100 kilometres as the crow flies, but is in fact around 160 kilometres. Likewise, Kokoda to Port Moresby is 120 kilometres direct but is judged to be around 200 kilometres actual distance. In short, this route requires over 260 kilometres of trudging.

The problem is securing supplies. This would not be an issue if there was a road suitable for motor transport. However, without so much as a pack-horse trail, the actual conditions will require all supplies to be transported by human carriers.

The current number of men on the front line would be approximately 5,000. Given an average daily food requirement of 600 grams per person, this would result in a daily supply requirement for the Force amounting to 3 tonnes. If each man could carry 25 kg of supplies, this would limit a days march in the mountains to 20 kilometres.

A round trip march to the front line would take 20 days if the Force were to advance to the saddle of the Owen Stanley Range approximately 100 kilometres from Buna. Given that supplies for each soldier would be depleted by 12 kg after 20 days, the amount he could deliver to the front line would be 13 kg.

Securing the daily 3 tonne supply for the Force would require approximately 230 carriers per day reaching the front line. This amounts in total, given the 20 day round trip, to a requirement for approximately 4,600 carriers. If the front were to advance to Port Moresby, some 360 kilometres distant from Buna, then to supply food alone would require 32,000 carriers.

If one considers munitions and other supplies, the requirement for carriers would be immense. Ultimately, the overland route is probably not possible unless a road for motor transport can be pushed out from Buna.