The previous war epic by Darryl F. Zanuck, The Longest Day (1962) was an extreme success. As stated by his son, producer Richard D. Zanuck, this was because it was about victory. He noted in contrast that Tora! Tora! Tora! is about defeat. Although the film made a great deal of money, it did nowhere near as well as The Longest Day. In Japan, however, the film was a smash. For the Japanese audience, it not only depicted a battle victory (after twenty-five years of films depicting defeat) but it also put the attack on more understandable footing; identifying not only the villains but also the motivation of those who believed that their actions were honorable.
The wounded sailor shown firing back at the strafing Japanese planes late in the film near the conclusion of the attack is based on Chief Ordnanceman John Finn, who was stationed at Kaneohe Naval Air Station on December 7, 1941. He set up a .50 caliber machine gun mount, and despite being wounded several times, fired back at strafing Zero fighters during the second attack wave, hitting several of them, and even shooting down one, piloted by combat unit leader Lieutenant Fusata Iida. Finn was later awarded the Medal of Honor for valor beyond the call of duty.
When Japanese characters refer to the date of the attack, they actually say "December 8." It's technically correct, as Japan is a day ahead of the U.S. It was translated as "December 7" in the subtitles to avoid confusing U.S. audiences.
The scene where the military band keeps playing "The Star Spangled Banner" even while they are under attack is in keeping with military code: when the US national anthem is played, it must be played through regardless under any circumstance. So, when the conductor starts frantically accelerating the piece's tempo as the Japanese attack begins, he is keeping to military protocol while trying to give himself and the band the soonest opportunity to take cover.
Of all the time and money spent by Akira Kurosawa, less than one minute of the film he shot is in the final release version.