The Marines Amphibious Assault on Tinian

In July of 1944, on the small island of Tinian in the South Pacific, U.S. Marines used reconnaissance pull to guide an amphibious assault that smashed through the weakest point in Japanese defenses and ultimately paved the way for the construction of an air base on the island that was within bombing range of the Japanese mainland.

Tinian was part of an island pair that would have to be assaulted in succession. The Marines plan was to take its sister island, Saipan, which was more heavily fortified and well within artillery range, first. After twenty-five days of brutal fighting and six thousand casualties on Saipan, the Marines turned their attention to Tinian, which was already home to one of the longest airstrips in the region and therefore the more strategically significant target. Under the command of Major General Harry Schmidt, the V Amphibious Corps s Second and Fourth Marine Divisions spearheaded the fighting. Seeking a decisive victory without the heavy casualties incurred at Saipan, Schmidt deployed multiple reconnaissance elements to pull his two divisions through gaps in the Japanese defenses.

Figure 11.1: Marines Amphibious Assault on Tinian, July 10 “11, 1944

The Opportunity . The Japanese surmised incorrectly that the Marines could not land in sufficient strength on Tinian s narrow northern beaches and therefore assumed a defensive posture to the south. Leaving the northern area of the island largely unguarded, the 8,350-man Japanese force built hardened pillboxes, constructed mazelike obstacles, and scattered mines in the southern area in the hope of denying the Marines the 39-square-mile island.

Decentralized Decision Making and Targeting Critical Vulnerabilities. Schmidt entrusted Navy and Marine Corps reconnaissance elements to identify the enemy s critical vulnerability, verify the activity and location of defensive forces, assist in the formulation of an attack plan, and select the openings through which the main invasion force would flow. During frequent aerial reconnaissance missions in the months preceding the landing, Navy and Marine Corps pilots discovered the critical vulnerability of the formidable Japanese defenses ”susceptibility to northern attack. And Marine infantry forces on Saipan confirmed this finding when they captured valuable Japanese planning documents that revealed the Japanese believed an amphibious assault on Tinian could come only from the south.

These initial discoveries prompted Schmidt to dispatch Navy underwater demolition teams and Marine Corps reconnaissance teams to swim ashore under the cover of darkness and examine the feasibility and safety of a northern landing. The Marines conducted beach reconnaissance and harbor surveillance, while the Navy conducted hydrographic surveys to identify beaches suitable for a division- sized landing. Together the teams inspected Tinian s sharp coral reefs, recorded mine locations, mapped attack routes, and provided eyes-on assurance that the North was indeed unoccupied by enemy forces. The teams ultimately selected two beaches, which were but 60 and 150 meters wide, respectively. ^[2] Upon returning from the mission, the relatively junior officers in charge reported the details directly to Schmidt and his naval counterpart , Admiral Richmond Kelly Turner.

Tempo ”Planning. Initial landing plans called for a southerly invasion; however, in light of his reconnaissance elements findings, Schmidt made a timely command decision and changed his entire amphibious assault plan. Within two weeks of the reconnaissance teams report, Schmidt, along with Turner, reoriented the invasion to the north and marshaled enough troops, ships, vehicles and supplies to make a major landing.

Focus. On July 24, 1944, Schmidt fully committed his two Marine divisions to the assault. Before the actual landing, the Second Marine Division and U.S. Navy conducted a full-fledged feint to the south, going as far as releasing assault craft from navy ships and heavily bombing the expected southern route to reinforce the Japanese belief that the attack would come from that direction. Then the Fourth Marine Division launched in landing craft from Saipan in the first shore-to-shore operation in Marine Corps history. The Fightin Fourth jammed more than fifteen thousand men, tanks, artillery, supplies, and vehicles through the two dangerously narrow beachheads. According to the Fourth Marine Division Association historical record, Never in the course of the Pacific war had a unit of division strength tried to land on any beach smaller than twice the size of these two beaches combined.

Tempo ”Execution. Schmidt s tempo rippled through his fighting force. Within nine hours of its landing the Fourth Marine Division cleared the beachhead. On the second day the Second Marine Division poured through the opening and joined the Fourth to fight off a series of Japanese counterattacks inland. Together the two divisions compressed the retreating Japanese to the south side of the island. After just eight days of fighting, the Marines claimed complete victory.

Incurring far fewer casualties ”327 killed and 1,771 wounded ”than they had on Saipan, the Marines totally overwhelmed the Japanese defenses and captured Tinian. On the Marines heels, Can-Do Navy Seabees built a strategic air base with six landing strips and turned the island into a staging point for follow-on Pacific campaigns and bombing raids on key Japanese targets.

Leadership Lessons

The Marines success at Tinian illustrates how decentralized decision making, targeting critical vulnerabilities, focus, and tempo can be combined to achieve reconnaissance pull. Schmidt s willingness to decentralize decision making allowed his pilots, reconnaissance teams, and infantrymen to act independently and identify the enemy s critical vulnerability to the north, thereby improving the odds of a successful landing. Moreover, his ability to react in real time to new information ensured that the emerging opportunity in the North did not slip through his grasp, and a willingness to overhaul his entire plan displayed remarkable flexibility on his part. Finally, his decision to send two entire divisions across two narrow beaches ensured maximum exploitation of the opportunity.

^[2] United States Marine Corps, History of the U.S. Marine Corps Operations in World War II: Central Pacific Drive , Volume III , FMFRP 12-34-III, 1966.