Toho's first major color war film is without a doubt one of the most impressive of their many 60's offerings. The only one I can think of this easily trumps this is their later BATTLE OF THE SEA OF JAPAN (1969) which is about the Russo-Japanese War. This is a world war 2 film and probably the quintessential film covering the two largest, most pivotal events of the Pacific theater - Pearl Harbor and Midway. These battles would be covered in several later American films but never with the gusto of this production.
This presentation of the Pacific Theater is a little different than us Westerners are used to. There's something shockingly surreal about seeing the main characters elatedly cheering the destruction of the Arizona, or referring to December 7th, 1941 as "a wonderful day". Unlike German or Italian war films to come over the years after the war, this film by a former Axis member is not a guilt-ridden depressing condemnation of the past. Instead, the Japanese (many of the cast and crew members were veterans of the conflict) seem to be quite proud of their effort, camaraderie, and achievements. The attack on Pearl Harbor is shown as a more-or-less unavoidable battle and a great victory. Little attention is paid to the fact that the Americans are totally oblivious to the fact they're at war before the bombs drop. The Americans are actually rarely mentioned by name, only as "the enemy" and never seen besides their planes, ships, and ground installations.
Little can be said about this movie without mentioning the brilliant effects work by Eiji Tsuburaya and Teruyoshi Nakano. Tsuburaya had made some of Japan's most impressive propaganda films during the war which recreated the Pearl Harbor attack, and here he gets to do the same but in color and with more money and a larger water tank. The 1/16th scale models look brilliant and the explosions and fires realistic enough for MIDWAY to steal 16 years later.
Dramatically the film comes off as a little stiff, though Natsuki gives an earnest performance as a young pilot. Mifune plays Yamagouchi with his usual gravitas, and many recognizable Toho stock performers pop up in small roles throughout. The film also suffers from its no-frills straight-forward retelling approach (much like the earlier film THE MYSTERIANS) which means there's not really any subplots or plot twists. Just action, effects, and historical reenactments to provide entertainment. It also suffers a lot of the same failings as other Toho films of the time with the tendency to reuse effects shots (sometimes twice in a row), lots of jump cuts (such as an explosion goes off, then another, but the camera does not move despite a lot of time being cut out between the two explosions), and a few dodgy miniatures.
The real star is the battle scenes; not just the brief Pearl Harbor recreation, but the drawn out Midway battle that takes up the whole second half of the film. Excellent music, cinematography, and wholly believable process shots. Overall a thoroughly impressive war film which is unfairly hard to find.