By Col. Joseph Alexander, USMC (Ret)

“It was an operation of one phase and one tactic. From the time the engagement was joined until the mission was completed it was a matter of frontal assault maintained with relentless pressure.”
—Lt. Gen. Holland M. Smith, USMC
Commander, Expeditionary Troops, Iwo Jima
Task Force 56 Action Report, March 1945

Iwo Jima was the most heavily fortified island the Americans would assault in World War II. The strategic benefits of acquiring airfields within fighter range of Tokyo would be significant—the risks in attacking that steep, volcanic fortress, “the Doorstep to Japan,” would be enormous. No U.S. amphibious force could have tackled this mission any earlier in the war. Seizing Iwo Jima would require full command of the air and sea, overwhelming firepower, imaginative naval campaign planning, seasoned shock troops, and violent, sustained amphibious execution.

Iwo Jima was a latecomer as a potential objective for U.S. amphibious forces. Many planners figured that the campaigns in the Philippines and Palau would be followed by a combined operation against Formosa. Others, including Fifth Fleet Commander Raymond Spruance, believed the wiser choice would be to strike north-by-northwest against the Volcano and Ryukyu Islands. Seize Iwo Jima, he suggested, then Okinawa, in preparation for the final invasions of Kyushu and Honshu.

Iwo Jima represented a major obstacle to the strategic bombing of mainland Japan by B-29s based in the Marianas. The island, lying about halfway between Saipan and Tokyo, contained an early warning radar system that provided Tokyo with an invaluable two-hour alert of each approaching B-29 raid. Further, Iwo-based fighters launched to intercept the incoming bombers, forcing them to fly a circuitous route, requiring more fuel and diminishing their payloads. Fighters on Honshu, alerted by Iwo Jima’s radar, would be waiting for the American bombers, forcing them to fly higher altitudes, further sacrificing bombing accuracy. After each mission, Iwo fighters sallied forth again to swarm around crippled U.S. Super-Fortresses struggling to return to the Marianas. And Japanese medium bombers staged through Iwo for damaging raids on the U.S. airfields on Saipan and Tinian, destroying more B-29s on the ground than Gen. Curtis E. LeMay’s crews lost during their strike missions. The vaunted strategic bombing campaign had proven a bust so far. Iwo Jima had to go.

On 3 October 1944 the Joint Chiefs of Staff directed Nimitz to capture the eight-square-mile island. With Halsey still mired in the “tar pit” of Peleliu, Nimitz gave the newest tasking to Spruance. Reduced to its nub, the Fifth Fleet’s mission was twofold: enhance the strategic bombing campaign; facilitate the ultimate invasion of the Japanese homeland. Nimitz emphasized speed of execution, as he had before Tarawa, saying: “It is a cardinal principle of amphibious operations that shipping be localized and exposed at the objective for the minimum possible time.” This guidance would prove increasingly difficult to honor: seizing Iwo would take five full weeks; Okinawa, twice as long.

Operation Detachment, the campaign to seize Iwo Jima, became of necessity a stepchild wedged between the larger campaigns of Luzon and Okinawa. This narrow window of time dominated the planning for Detachment. Even as late as 1944-45 America lacked the resources to conduct two, simultaneous, full-scale amphibious operations in the Pacific. The JCS twice postponed D-Day for Iwo because slow progress in Luzon delayed the turnover of naval gunfire support ships and landing craft from MacArthur’s forces to the Fifth Fleet. Nor was there any slack at the other end of the schedule. Spruance had to complete the seizure of Iwo Jima and reposition his amphibious forces to support the Okinawa campaign well before 1 April. That was the latest date Okinawa could be invaded without incurring undue risk from the summer typhoon season.

These time constraints did not unduly bother Spruance. He knew each of his principle task force commanders to be a veteran of urgent planning and hard campaigning in the Central Pacific. He led a seasoned, proven team. Marc Mitscher would again command the Fast Carrier Task Force (TF 58); Kelly “Terrible” Turner, the Joint Expeditionary Force; “Handsome Harry” Hill, the Attack Force. Rear Adm. W.H.P. “Spike” Blandy, highly regarded for his cool-headed handling of an amphibious group at Saipan and Tinian, would take command of the massive Amphibious Support Force (in effect, the “advance force commander”).