Earlier this month, the world gave a tremendously deserving tribute to the brave servicemen who stepped foot into battle on the beaches of Normandy on June 6, 1944. This month also marks the seventy-fifth anniversary of another amphibious assault, half a world away from France: the US landings on Saipan on June 15, 1944. If Operation Overlord was the decisive operation of the European theater, Operation Forager—the Allied campaign to seize the Mariana islands from the Japanese—was the decisive campaign of the Pacific. The contest on land, at sea, and in the air—despite the passing of three-quarters of a century—provides lessons for the future of multi-domain operations. It illustrates the need to balance offensive striking power with operational reach, especially in campaigns that span the Indo-Pacific. It also affirms that joint doctrine, training, and relationships must be continuously maintained in order to promote the mutual trust and shared understanding required to conduct mission command during multi-domain operations. Lastly, the technological advances in long-range weaponry of the era, combined with the island-hopping strategy of the Pacific campaign, highlights modern-day opportunities in modernization investment for the Army of today.
Ironically, the best thing that happened to the soldiers and Marines who landed on Saipan had very little to do with events on the ground. Rather, the cataclysmic naval battle of the Philippine Sea, which took place on June 19–20, 1944 less than four hundred miles from Saipan proved decisive in the elimination of the Japanese naval forces’ ability to conduct offensive maneuver in the Pacific theater. Adm. Raymond Spruance, commander of the US 5th Fleet, knew that the Japanese carriers intended to use their aircraft’s greater range, in combination with local land-based fighters, to execute a devastating attack on his vulnerable transport and cargo forces anchored off Saipan—over one thousand miles from the nearest friendly base at Eniwetok. With this information, Spruance had the opportunity to maneuver his aircraft carriers to close the distance and attack the Japanese first. However, he was under tremendous pressure to execute multiple, nearly simultaneous operations in hostile waters far from any friendly logistical support. Adm. Chester Nimitz, commander of the Pacific Fleet, wanted to know when Spruance would commit to an invasion of Guam—and this was in addition to Spruance’s responsibility for defeating the Japanese 1st Mobile Fleet and the garrison at Saipan.
With these competing demands in mind, Spruance avoided the bold offensive overreach advocated by his subordinates, and instead ordered Adm. Marc Mitscher, commander of the aircraft carrier–based Task Force 58, to fight defensively and preserve his operational reach and capability. Mitscher, a naval aviator by trade, strongly advocated for a bold offensive thrust toward the Japanese and away from Saipan, but complied with Spruance’s orders. Mitscher optimized his formation by using multiple forms of contact to blunt the Japanese naval offensive. By air, his expert pilots deftly outmaneuvered their Japanese counterparts with an 11:1 win/loss ratio. On the surface, he used a well-placed destroyer screen as a “flak net,” obliterating the majority of incoming enemy aircraft that managed to make it past his pilots. Underneath the sea, his submarines took advantage of the Japanese fleet’s preoccupation with the air campaign by quickly moving into position to score crippling hits against the Japanese carriers Shokaku and Taiho. Perhaps no naval victory throughout the entire twentieth century was so one-sided, as the US Navy destroyed three Japanese carriers and five oilers, and damaged numerous other vessels, without losing a single ship to enemy attack. Most importantly, the US forces destroyed nearly four hundred Japanese aircraft and pilots, leaving the Japanese fleet’s commander with only thirty combat aircraft available for immediate operation, while the US forces maintained nearly the entirety of its aircraft complement.
What should commanders of future US operations take away from this maneuver? Balancing a well-integrated defense may be the key to preserving operational reach and capability. Had Spruance decided to brashly chase after the Japanese fleet without confirming its location, he may have fell victim to Japanase decoy tactics, leaving his ships prey to ambush and his ground forces isolated at Saipan. Future US operations in the Pacific must similarly manage the risk of strategic overreach by carefully balancing bold offensive operations with expert defensive operations. No matter which types of operation the military may conduct, though, masterful convergence of capabilities in all domains will force the enemy into overwhelming dilemmas.
As the US armed services continue to develop the concept of multi-domain operations, a well-established and trained mission-command system will become increasingly important. Specifically, “building cohesive teams through mutual trust” and “creating shared understanding” will be the two most critical principles to develop—especially between units from different services in a joint context. Army, Navy, Air Force, and Marine forces, each with their own unique capabilities, will share operational environments as large as the Pacific Ocean and as small as a tiny natural or manmade island. On Saipan, in June 1944, systematic failure in mission-command principles led to a national crisis between the joint services. Marine Lt. Gen. Holland M. Smith, commander of the ground force assault on Saipan, ordered the 2nd and 4th Marine Divisions to attack across the relatively flat western and eastern coastlines of Saipan, while directing his reserve, the Army’s 27th Infantry Division, to attack across the steep, rocky, and treacherous middle section dominated by Mt. Tapochau, the island’s highest point. As the two Marine divisions advanced from their respective sections of coast, Japanese artillery, mortars, and machine guns entrenched throughout the mountainside pinned down the Army division, bringing its advance nearly to a standstill. This created a dangerous “U-shaped” salient that exposed the Marine divisions on either side to potentially crippling counterattacks.
In an act of resentment toward Army forces and with undue haste, Smith relieved Maj. Gen. Ralph Smith (no relation), commander of the Army 27th Infantry Division. The decision to replace the division commander with a non–battle tested replacement made almost no difference to the Army division’s advance; it was still faced with the same daunting tactical challenge. However, it caused a national outrage and traumatic institutional rift between the Army, Navy, and Marine Corps. The Army convened an exclusive internal review of Ralph Smith’s relief, with testimony limited to Army officers and official record, determining that the Marine general was not justified in taking this action. Army general officers wrote letters to the convening boards stating that Army units should never serve under the Marine general again. Time and Life magazines printed articles taking the Marine Corps’ side, claiming the 27th Infantry Division’s soldiers were “frozen in their foxholes” and had to be rescued by the Marines. Army Gen. Douglas MacArthur, with Adm. Nimitz’s consent, countered by refusing permission for Lt. Gen. Smith to witness the surrender of the Japanese aboard the USS Missouri in September 1945.
Institutional spite and acrimony between the services akin to the Smith vs. Smith controversy could undermine the entire mission-command foundation required to converge warfighting functions of the separate services throughout multi-domain operations. To build teams through mutual trust, the newly created multi-domain task forces must constantly seek new and expanded opportunities for joint and partnered services to train together at echelon. Army and Marine units deployed in Europe, for example, should train together. Another possibility is for Army and Marine attack helicopters to conduct periodic training in support of each other’s ground forces in an effort to learn how their different capabilities can be tailored to fit the needs of one another’s mission requirements.
Creating shared understanding requires leaders at echelon to study sister service’s doctrine in conjunction with that of their own. The Army and Marine Corps approach to tactical and operational problem solving (in conjunction with all other services) yields many historic differences that provide opportunity for cognitive development among joint service leaders. Steeped in Army doctrine, the 27th Infantry Division fought in a deliberate combined-arms fight, with entire battalions moving slowly together on a large front units maneuvering to a flanking position supported by massive artillery bombardment. By nightfall, Army units tended to withdraw to more secure positions behind the front line to avoid envelopment and set the conditions for future wide maneuvers. This methodical, deliberate method of attack for Army units was well suited to the clash of large continental armies, which minimized casualties over lengthy campaigns in time and operational space. In contrast to the Army, Marine Corps units were sustained and supported by a highly vulnerable naval fleet, and therefore emphasized rapid, direct assault. The Marine Corps deliberately accepted the higher risk of greater initial casualties, which would be mitigated by avoiding a lengthy campaign in a condensed operational environment. In preparation for the unknowns of a future multi-domain operation, Army units should conduct beach-assault landings with their Marine counterparts at major amphibious training exercises. Soldiers and leaders will inevitably learn a great deal from the required joint coordination measures, while also appreciating both the simplicity and difficulties of a direct assault against a fortified position. Marine units, in turn, should have the expanded opportunity to continue conducting wide-scale maneuvers with Army units at the various combat training centers.
The island-hopping campaigns in the Pacific theater provided the joint forces an unprecedented opportunity to project power across the Pacific by sea and air. Operation Forager and the defeat of the Japanese garrisons at Saipan and the adjacent Mariana Islands opened the window of opportunity for relentless B-29 bomber raids over the Japanese home islands. Today, the Army is able to project significant power through the use of ground-based weaponry, to include medium-range ballistic missiles, new fixed wing UAVs, stealth rotary-wing helicopters, electronic warfare, and other developing stand-off platforms that did not exist during the Pacific campaign in World War II. With rising competition from Chinese and Russian weapons developments, the Army must consider making modernization its top funding priority to ensure successful completion of much-needed capabilities for the ground domain.
The US military’s failure to modernize ahead of the Japanese carried severe consequences early in the Pacific campaign. The Mark 14 torpedo, developed in 1931 and used by the Navy’s submarine fleet, contained severe design flaws that were only discovered during the crucible of naval combat in World War II. Compared to the world-class array of Japanese torpedoes, which swam with deadly precision and superior range, the Mark 14’s tendency to shoot ten feet beneath the target, its failure to detonate on impact, and even the frequency with which it would turn around toward its own submarine revealed glaring setbacks in US naval modernization. In the skies over the Pacific, the US Navy’s F4F Wildcat was supremely outclassed by the Japanese Zero in range, maneuverability, and climbing rate. While expert Navy pilots adopted tactics to leverage the Wildcat’s better armor and armament for improved survivability against the Zero, it wasn’t until the 1943 introduction of the F6F Hellcat that the US Navy could affirmatively field a fighter aircraft markedly superior to the Japanese Zero. While the two examples above are specifically related to modernization setbacks within the Navy, the multi-domain consequences provide a highly cautionary tale to the Army, which continues to make readiness, rather than modernization, its top priority in an uncertain congressional budgetary environment. The Chief of Staff of the Army’s drive to achieve a “two-thirds/one-third” readiness standard (whereby two out every three active-duty brigade combat teams are ready to “fight tonight”)—despite reassurances that the Army is already prepared to face any opponent—seems counterproductive when the Army is outranged and outgunned across numerous warfighting functions.
While the US military remains the most formidable fighting force the world has ever known, the joint force will continue to experience great challenges in projecting power across the Indo-Pacific in competition with a rising China. The US military must find unique and creative solutions to balance striking capability with operational reach. It must continue to build joint doctrine, training environments, and relationships in order to promote the mutual trust and shared understanding required to conduct mission command throughout multi-domain operations. And the joint force, and the Army in particular, must put serious consideration into prioritizing the future fight through modernization efforts, developing new concepts, platforms, and weapons for the warfighter of tomorrow.