A Marine division combined three infantry regiments, each of roughly three battalions, with an artillery regiment and supporting services. The First Marine Division also had attached defense, parachute, raider, amphibian-tractor, aviation-engineering, pioneer, medical, special-weapons, and tank units. These elements gave it capabilities beyond its infantry strength. Over the campaign, the Second Marine Division reinforced the effort, and the Americal and 25th Infantry Divisions helped relieve the Marines. Japanese reinforcements, including the 2nd (Sendai) and later 38th Infantry Divisions, arrived piecemeal as transport became available. The comparison concerns the ability to bring a complete force to bear, rather than just nominal troop totals. American supply still ran short and the early operation had serious problems, but the Americans learned how to sustain the formation they had brought.
Notable Point · 35:22-38:59
Marine support units and piecemeal Japanese reinforcement
The Marine division arrived with artillery and specialist support, while Japan struggled to deliver successive formations through limited transport capacity.