Ken Watanabe read actual letters sent by Imperial Japanese Army General Tadamichi Kuribayashi to his family from Iwo Jima while preparing for his role.
Most of the young cast knew nothing about the incidents on Iwo Jima, as it is not taught in Japanese schools.
When word spread that Ken Watanabe had been cast in the lead, virtually every young actor in Japan let it be known that they were interested in working on this movie.
The original plan was to tell both sides of the story in one movie. As production developed, it became obvious that there was too much to tell, and that the two separate cultures created very different storylines.