The problem with the early counterattack by the Japanese is full of problems, as is any counter attack they make. The first is that only about a third of their troops are really infantry. The rest are manning heavy weapons in fixed positions. The next problem is that the Japanese lack virtually any mobile heavy weapons. They have no submachineguns. They have few machineguns that can move with the advance. Outside the puny 50mm grenade lauchers they have no mobile fire support and no way to communicate to get fire support. This limits virtually any offensive action to essentially just bolt action rifles, bayonets and hand thrown grenades of dubious quality.
Another problem is that the defenders are more or less homogeneously spread across Betio. That is, they lack concentration at the point of decision. The Japanese did not have nor did they plan for a mobile reserve force of any size to react to landings. If they had it would have been vulnerable to the preliminary bombardment to some degree. So, in order to launch a counter attack the officers would have had to send runners, communicate with, etc., the various groups of men and move them under fire to a central location to concentrate for the assault. This would have taken alot of time. It also would have required the commanders have a pretty good idea of where the Marines had landed and where to direct the attack. If the Japanese choose wrong they might expend their forces for no gain or they might send them against a strong point in the Marine lines to be exterminated.
So, the Japanese in order to launch a successful counter attack have to: Achieve a concentration of men at a good point to launch the attack with sufficent numbers present to actually overcome the landing forces at the point of decision. The question is, how many men are required to do this out of the roughly 1500 available for the task and can that many be gotten togeather and orgainzed to perform the task?

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