What was the timetable for the arrival of the 100,000 man Japanese garrison at Rabaul?

Question

Early in 1942, the Japanese seized the natural port of Rabaul on New Britain Island. This was to protect its existing base at Truk, in the Carolines, and also to provide a forward base for operations in New Guinea, the Solomon islands, and points further south.

Over time, the garrison at Rabaul rose to over 100,000 men. (It was isolated and bypassed by the Allies, and the forces were eventually left to "wither on the vine.") If there were actually 100,000 men on Rabaul at the appropriate time, some 50,000-75,000 of them could have been used to help the Japanese win key battles in New Guinea or Guadalcanal in the fall of 1942.

This did not happen of course, and I wonder why. The most obvious explanation is that most of the "100,000" men arrived on Rabaul after the key battles had been decided in the Allies' favor. A second, and related explanation is that Japanese soldiers sent to the South Pacific were sent first to Rabaul, for distribution to the other areas as needed. Then Allied naval and air activity hindered this "distribution" process, leaving an inordinate number of Japanese troops backed up on Rabaul. This "hindering" process, of course, increased as time went on.

So when did Japanese reinforcements actually arrive on Rabaul, and what did this mean for Japanese activities in the region?

Answer 1

The question about the timetable is difficult to answer. However, the question lagging behind could be clearly answered: your second hypothesis is true.

The battle of Guadalacanal was fought by the Japanese mainly with forces numerrically inferior to the American marines based on the island. The top number was 20 000 during what is called the Battle of Henderson Field (but is, in reality, the terrestrial part of the naval battle of Santa Cruz). Compare this top number in Guadalcanal to the 100 000 men in Rabaul and you see that the problem was mainly about having enough soldiers at the same time on Guadalcanal, and this problem lied in the Japanese naval logistic.

For the battle of New Guinea, this is a similar issue: at first, the battle w as a matter of small forces whose number was limited by the logistic in the central mountains of New Guinea. Later on, the Japanese had to defend their bases on the North Coast of New Guinea, and they failed because those bases were cut off from Rabaul and other bases that could provide them with reinforcements.

Eventually, why were there so many men in Rabaul? For two reasons:

• First, the Japanese used it at a central base from where soldiers were sent to battlefield (but they mostly sank on the path to the battlefield)
• Second, the Japanese used Rabaul as an air base so the Allies were only lately able to block it, because it has a huge number of airplanes and boats (contrary to the battlefields Guadalcanal and Lae)