Battleships and cruisers unleashed thousands of shells on the eight-square-mile volcanic island, targeting the extensive tunnel and bunker network Japanese General Tadamichi Kuribayashi had built into Mount Suribachi and the surrounding terrain. Despite the intensity, most fortified Japanese positions survived deeply buried underground, setting the stage for one of the bloodiest amphibious battles of the Pacific War when Marines landed on February 19.
For three days before the landings, American naval guns turned Iwo Jima's black volcanic sand and scrub into a moonscape of craters. Battleships including the USS Tennessee and USS Idaho fired round after round at suspected gun emplacements, yet Kuribayashi's defense strategy had anticipated exactly this. Rather than defend the beaches, he ordered 21,000 men into 11 miles of tunnels and reinforced concrete bunkers, some five stories deep, designed to withstand precisely this kind of bombardment.
Aerial reconnaissance photos convinced American commanders the defenses had been sufficiently softened, but the underground fortifications remained largely intact. Kuribayashi had explicitly forbidden the wasteful banzai charges that had squandered Japanese manpower on other islands, instead ordering his men to exact maximum casualties from hidden positions, a defense in depth that would make Iwo Jima catastrophically costly for the Marines who landed three days later.
The bombardment reflected a mismatch in expectations that would haunt the entire battle: American planners believed Iwo Jima would fall within days, while Japanese defenders were prepared to fight to near-total annihilation from tunnels that thousands of shells had barely touched.
Key people: Tadamichi Kuribayashi, Raymond Spruance