Previous post: Tarawa
In the early 1930s at Quantico Virginia, Fleet Marine Force leaders began to work on the problems of conducting amphibious offensives, which they found required new combat techniques and a high degree of combined-arms coordination, as well as special landing craft and weapons. The Tarawa invasion of November 1943 showed that Nimitz's navy and marine forces still had much to learn, but by the time of of their assaults on the Mariana's the next summer they had mastered the intricacies of amphibious warfare.
D. Clayton James, "American and Japanese Strategies in the Pacific War," Makers of Modern Strategy
This did not happen by accident. Col. Joseph Alexander notes that the commitment to learning the right lessons quickly came from the very top:
Within a few weeks, the navy had built exact replicas of the defenses and started to work improving on improving the fire support tactics and weapons. In addition, 2d Marines produced fourteen reports on lessons learned. The first was submitted on 27 December and the last on 13 January 1944.
Before leaving reeking Betio, Nimitz ordered the preparation of engineering drawings of the Japanese fortifications on a priority basis.
Unfortunately, the US Army did not possess the same eagerness to learn from the experience of Tarawa.
Even worse, Bradley, who had no experience with amphibious landings, did not take advice from officers who had seen service in the Pacific. Moreover, he disliked the Navy and was uninterested in their work on fire support and ship to shore movements under enemy fire. At Tarawa the Marines learned that amphibian tractors were worth their weight in gold. Bradley left 300 amtracs in England. Nor did Bradley see the value in the specialized engineering vehicles developed by Gen. Sir Percy Hobart to overcome the extraordinary challenges presented by the German beach defenses.
"The one marked weakness among the top Allied officers lay in the commander of American ground forces, General Omar Bradley. Bradley was an unimaginative and uninspiring commander, who had already proven to possess a streak of jealousy for subordinates more competent than he was. In addition, he was an Anglophobe who exacerbated tensions with the British."
James Lacey and Williamson Murray, Moment of Battle: The Twenty Clashes That Changed the World