Question

Why did the Allies capture so few Japanese soldiers when they attacked Iwo Jima?

Answer 1

Short answer: Because the Japanese defenders at Iwo Jima were prepared and ordered to fight to the death, used elaborate fortifications and tunnel systems that favored killing over capture, and were culturally and psychologically conditioned to avoid surrender. Those factors, combined with heavy Allied firepower and the nature of close-quarters fighting, meant very few survivors ever came out to be taken prisoner.

Details:
- Japanese doctrine and orders: Commanders (notably General Kuribayashi) deliberately adopted a defense designed to bleed the Americans rather than seek maneuver or breakout. Imperial Japanese military culture and official policy strongly discouraged surrender; troops were indoctrinated that surrender was shameful and dishonorable. Many were explicitly ordered to resist to the death.
- Fortifications and tunnels: The Japanese built an extensive network of caves, bunkers and tunnels. Defenders could fight from protected positions and then vanish into the underground system, making it easy to resist until killed and hard for attackers to force surrenders or round up prisoners.
- Close, brutal combat and overwhelming firepower: Naval bombardment, artillery and air strikes plus infantry assaults caused high rates of death and destruction. When positions were overrun, defenders were often already killed; when wounded, many were finished off in close combat or chose suicide rather than capture.
- Fear of mistreatment and propaganda: Japanese troops had been told Allied captors would torture or mutilate them, and some incidents in the Pacific fed a mutual fear and brutality. That reinforced the unwillingness to surrender.
- Practicalities of the assault: Capturing prisoners requires opportunities for organized surrender and secure handling. On an island where most defenders were isolated in hidden positions and large parts of the battle were chaotic mopping-up of caves, those opportunities were rare.

Result: of roughly 21,000 Japanese on Iwo Jima only a few hundred surrendered; the vast majority died in their positions or by suicide. The same combination of doctrine, defenses and cultural pressure produced low prisoner rates in several hard-fought Pacific island battles.