U.S. Army Divisions of the Pacific War
Stephen R. Taaffe, Casemate, 2024, 256 pages
Book Review published on: September 18, 2025
As the U.S. military shifts focus to the Pacific Theater of Operations (PTO) it is enlightening to study how we have historically conducted large-scale combat operations in a multidomain style of combat in the past. Stephen R. Taaffe's U.S. Army Divisions in the Pacific War examines the employment of the twenty Army divisions that operated in the PTO in World War II. Taaffe provides insights and observations that shed light on the organization, employment, and leadership challenges faced by the Army as it helped to systematically defeat the Imperial Japanese Empire between 1941 and 1945, and it draws lessons that apply to modern challenges.
Most consider World War II in the PTO to be primarily a U.S. Navy/Marine Corps war, but the reality is far different. Six Marine divisions participated in World War II in the PTO (mainly in the Central Pacific), while twenty Army divisions were employed there. There were 1,770,000 soldiers compared to 484,000 marines. These divisions were employed individually in corps and even in field armies, and consisted of regular Army, Army National Guard, and draftee divisions. The differences in the combat performance of these divisions are noted throughout the study.
The PTO was operationally divided into two theaters as the United States moved toward Japan. These were the Pacific Ocean areas, including the critical Central Pacific (primarily a U.S. Navy/Marine Corps theater) under Chester Nimitz, and the Southwest Pacific Area under Douglas MacArthur. While the book does cover U.S. Army participation in the Central Pacific (Saipan, Guam, Eniwetok, Kwajalein), the primary geographic area covered is MacArthur's Southwest Pacific theater, where the bulk of Army units were deployed. Almost all the long-term campaigns in the Southwestern Pacific theater including the Philippines, New Guinea, and the Isolation of Rabaul were Army-centric or Army-exclusive.
Of special note is the author's emphasis on unit's combat debuts. Almost universally (with a few notable exceptions), units performed poorly in their initial combat encounters versus the Japanese. Casualties tended to be high, the progress slow and methodical, and units struggled with basic operational tasks. Specifically, units lacked aggressiveness and were not proficient at the complex timing and coordination required by multi-domain combat at that scale. It was only after units had been "blooded" in combat that their effectiveness began to improve (often rapidly).
Leadership was also impactful, and many examples of this are captured. Units usually reflected the personalities of their senior leaders, and how this "force of will" drove the units. Over a long enough time, this would eventually become unit "culture" and would manifest in the levels of aggressiveness, professionalism, discipline, initiative, and tenacity in combat. Having the right leader at the helm was therefore crucial, and many division commanders who started the war were rapidly relieved when they failed to measure up.
Senior commanders (corps and theater commanders) also are covered. Many of them were harsh taskmasters, demanding levels of aggressiveness that often exceeded what the division commanders were comfortable with. These were not pleasant men, yet their ruthless and relentless drive to finish the war were crucial (in retrospect) in ending the Pacific War before America's national will was expended. Also of note was the need and willingness to relieve subordinate commanders who didn't have the traits required for the successful conduct of war at the operational level.
In the PTO, success was not just measured in "victory" over an opponent; rather, how fast, and at what cost victory was achieved. For this reason, operational level commanders (at corps level and above) were usually pressing for tactical operations to be conducted far more rapidly and aggressively than most divisions were comfortable with. This led to a counterintuitive effect: speed (and losses) at the tactical level usually translated to quicker and cheaper victories at the operational level.
A particular challenge discussed was the leadership difficulties encountered by National Guard divisions. Simply put, the qualities it took to raise and run a National Guard division in peacetime were not the same as those to command it in wartime. The community foundation of National Guard units brought many inherent strengths with it, but when it came to command, the hometown familiarity between commanders and subordinates proved to be a major obstacle. Almost all ARNG commanders at the divisional level (with one notable exception) were eventually replaced due to this issue.
Contrasting that is draftee divisions. These could be reasonably expected to perform poorer than the regular Army and even the National Guard divisions, since they were new from the ground up units. The reality was a bit different. After the usual first time in combat issues, most of these units settled in and became excellent, reliable divisions. They didn't have the higher echelon leadership issues that had crippled the National Guard divisions.
An important theme that runs throughout the book is the quest to get all divisions to "veteran" status, where they could be reliably competent at the tactical level. Other topics include dealing with a harsh operational environment, introducing new units to combat, the value of combat experience, unit reconstitution, and factors that make a "good" unit. Lastly, there is coverage of many of the moral aspects of combat that are often ignored in historical studies. These include the effects of morale, esprit, cohesion, discipline, grit/tenacity, professionalism, and the impact of lower-level officers and NCOs.
This is not a casual history of the Army in the PTO. It assumes a basic level of understanding World War II and Army operations. While the study does not cover the organization, manning, or training of the divisions (all of which was conducted stateside), Taaffe capably addresses the combat employment of the divisions, their relative combat effectiveness, and the reputations they gained as fighting units with professional insight and analysis. For readers with the desire to harvest them, there is a rich crop of lessons on modern organizational and operational challenges that are currently under address by the U.S. Army.
Book Review written by: Col. Scott Cunningham, U.S. Army, Retired, Leavenworth Kansas