Overview
Lieutenant General Tadamichi Kuribayashi’s preparations for the defense of Iwo Jima began in May 1944, when he was summoned by Prime Minister Hideki Tōjō and ordered to hold the island to the last. Arriving in early June, he found its air strength already collapsing; by July, American naval bombardment had destroyed all remaining aircraft and surface structures. Expecting an eventual invasion, Kuribayashi evacuated civilians and rejected the traditional water’s‑edge defense, noting that American firepower would annihilate beach positions. Instead, he planned a deep, attritional defense, placing artillery on Mount Suribachi and the northern high ground, while constructing only token beach pillboxes, all of which were destroyed by bombardment.
From mid‑1944, Japanese engineers transformed Iwo Jima into an underground fortress. Mining teams designed extensive tunnel networks, and reinforcements steadily arrived: the 2nd Independent Mixed Brigade, the 145th Infantry Regiment, naval construction units, and later Rear Admiral Rinosuke Ichimaru with aviation personnel. By late 1944, the garrison exceeded 12,000 men, supported by reinforced concrete blockhouses and a growing tunnel system that eventually reached more than 18 km in length. Conditions for workers were severe, with extreme heat and sulphur fumes forcing constant rotation of labor details.
Artillery strength expanded dramatically, including more than 360 guns of 75 mm or larger, heavy mortars, naval guns, anti‑aircraft weapons, and rocket launchers. The 26th Tank Regiment arrived without its original tanks—lost when their transport was sunk—but eventually received replacements, which were dug in as static, concealed positions.
By early 1945, Kuribayashi commanded 21,000–23,000 men. His final defensive plan forbade counterattacks and banzai charges, relying instead on mutually supporting strongpoints in depth. Artillery was ordered to remain silent during pre‑invasion bombardment, and the beaches were to be left undefended until the Americans advanced inland, where concentrated fire would begin the systematic attrition he intended.