Japanese combat deaths numbered three times the number of American deaths although, uniquely among Pacific War Marine battles, American total casualties (dead and wounded) exceeded those of the Japanese.
[11] Of the 21,000 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.
[1] The majority of the remainder were killed in action, although it has been estimated that as many as 3,000 continued to resist within the various cave systems for many days afterwards, eventually succumbing to their injuries or surrendering weeks later.
[1][12]
no plausible circumstance in which the Americans could have lost the battle.
https://en.wikipedia.org/wiki/Battle_of_Iwo_Jima