Complex sentence: Of the 22,000 Japanese soldiers on Iwo Jima at the beginning of the battle, only 216 were taken prisoner, some of whom were captured because they had been knocked unconscious or otherwise disabled.
Split into simpler sentences: Of the 22,000 Japanese soldiers on Iwo Jima at the beginning of the battle, only 216 were taken prisoner. Some of them were captured because they had been knocked unconscious or otherwise disabled.