オーストラリア戦争記念館の豪日研究プロジェクト
Australian and Japanese attitudes to the war
Southern Cross: XII Activity of Nakai Detachment in the Bogadjim Valley area

The region between the Finisterre Range and the Adelbert Range – in other words, the narrow Bogadjim River valley – is the quickest route between the Madang area, the Nadzab Plain and the rear of the Lae area. It was therefore a valuable area for the Hagen Tableland, which could be used for an advance on the enemy’s air base. So it was essential, from a strategical warfare point of view, to make it secure. But to make sure of securing it, as we had learned from previous experience, roads were an essential condition. The army decided to go along this valley and built a motor road. The 20th Division main strength advanced to the Madang area, H.Q. 4th Engineers (C.O. Major-general NISHIHARA, later Major-General YAMADA) and the 2nd Field Road Unit were assigned to them to hasten the completion of the road.

Originally, after evaluation of aerial reconnaissance it was thought this would take three months, but it was possible to shorten this period. As a result of subsequent developments, it happened that an infantry regiment had to be sent quickly to Finschhafen; it was just then the rainy season in this district, and the newly reconstructed bridge was washed away, there was a landslide and they were unable to advance as anticipated; however the officers and men made efforts, forgetting their tiredness, and in late June 1943 they succeeded in arriving at the watershed, which they called Kanki (T.N. – "Joy") Mountain because from it they were able to gaze down on the Ramu River Plain. The natives had never before seen motor vehicles and their eyes popped at the sight.

Already two thirds of the distance was completed. Since the remaining one third was a downward slope, in the opinion of the troops they had already swallowed the Nadzab Plain. While this road was being built, there was an urgent request for the Finschhafen area defence, and events such as the transfer of H.Q. 4th Engineer regiment to western New Guinea, occurred in succession. The army decided to continue building the road, using the main strength of the 18th Infantry Regt Engineer Units, and Maj-General NAKAI, the commander of 20th Infantry Group, was instructed to supervise it. However, with the situation in the Lae area being reported more critical every moment, and with Australian troops appearing sporadically on the Ramu River track in the Hagen Tableland, Maj-Gen NAKAI was not able to continue the building of this road. He used the main strength to build positions, and each unit to oppose the enemy in the Ramu river valley; the construction of the road henceforth changed to that of a packhorse road. Then on 4th September, with the break-through by enemy Group and the parachute landing on Nadzab, as I have reported, the situation changed suddenly.

At the beginning, the Army told the Nakai Detachment to prepare to receive Moto Group who were to transfer there, but when it became known that Moto Group planned to make the Sarawaged crossing, this duty was amended and instead it was decided to try a feint attack on the plain, to restrain the enemy who were pressing at the rear of Nonaka Group.

This operation produced unexpected results. This was because the enemy, afraid for Nadzab airfield, kept coming out in fast vehicles to block our troops at a distance.

So our vehicles and theirs clashed near Kaiapit, an important village on the Nadzab Plain. In this encounter, our vehicles had the advantage of the initiative, but it was a plain with tall grass, and it was very bad for our forces that they did not have the advantage of having visibility, and the enemy sent planes over all the time to bomb our various places, and this was most disadvantageous.

Originally the object of this battle was not to decide victory or defeat, but merely to confine the enemy to the area mentioned. So not only did Nakai Detachment inflict considerable losses by suddenly attacking the enemy’s positions at night, at dusk or at dawn, but they also became exhausted in pursuing the enemy’s land units. The enemy decided to wipe out this raiding force on the plain; they mobilized all their planes and from sunrise to sunset soared over the plain, increasing the firing attacks. This continued for more than ten days, and it is no exaggeration to say that the maximum was estimated at a thousand planes in one day. The enemy were very much afraid at the appearance of Nakai Detachments.

So that they could quickly build an airfield on Nadzab plain, the day after they dropped the enemy started burning the grass and the smoke from the flames covered the Nadzab plain. The enemy were probably afraid the detachment would penetrate this airfield. And this was the reason they did not come out to take positive action against the Nonaka Group. The enemy plan was to make rapid progress with the airfield. The fighting was being carried out mainly by aircraft, and the duty of the land units was only to protect the airfields.

The enemy who had occupied Kaiapit pressed against Nakai Detachment and at the end of September, beneath our troops’ gaze in their positions in the Kanki Mountain region they were building the airfield and deploying their artillery, so that it was apparent that a comparatively big offensive was to begin.

As it came October the enemy starting aerial bombardment of Bogadjim Kanki Mountain road, especially the bridges, in order to cut off our supplies by striking at this weak point, the narrow valley road. I have already explained how difficult it had been to construct these bridges, and the maintenance of this motor road was also difficult; it became necessary to use horses; but as there were not sufficient horses, it finally became necessary to revert to a primitive form of transport – the shoulders of men. It was a sad blow to Chief of the Engineer H.Q. YAMADA, who had smilingly gone to the new operational zone.

If there had been a respite for five or ten days it would have been possible to make counter-measures, but it was only natural that their energy should be exhausted after one month, two months of continual attacks. And enemy planes were busy attacking Nakai Detachment’s carriers.

I inspected the construction of this highway, and it was a fine road crossing the left bank mountain stream and cutting off the right bank precipice, going from this side of the Bogadjim valley to the other side – the terrain was rather like near Otsuki and Saru bridge on the Chuo Line. But now the efforts of officers and men had become fruitless. Even more intense than the bombing of the bridges was the bombardment of our positions. In addition, squalls were a speciality of the Finisterres. Our crumbling positions were buried in squalls, and ran with water, so that there was no place to stand. And the difficulty of repairing the positions was made doubly difficult because the work had to be done under the enemy’s direct observation.

Supplies and carriers suddenly dwindled to about one third of before, and there was a grave shortage of food.