Gamera the Giant Monster (1965) directed by Noriaki Yuasa
Cold War tensions over the Arctic are high. A U.S. aircraft shoots down some unidentified planes invading U.S. airspace. Since every military airplane in the 1960s carried atomic weapons, the crashing ship causes a large explosion that cracks the ice and sends radiation below. The blast revives Gamera, a saber-toothed, sixty meter tall turtle that can walk on its hind legs, breath (and eat) fire, and fly through the air. Gamera attacks Japan, which uses its military might and its scientific prowess to stop the monster. Both fail, forcing them to establish an international committee of scientists who craft an ultimate plan to foil the unstoppable terrapin, the mysterious Plan Z.
If that wasn't enough plot, this b-movie has a b-story. A small boy is fascinated with turtles and is forced by his family to free a pet turtle he named "Pee Wee." He happens to release Pee Wee on the same beach where Gamera shows up, convincing him that Gamera is Pee Wee all grown up and that Gamera will cause no harm. Gamera does save the boy later, endearing the giant turtle all the more to the young boy, who improbably keeps showing up throughout the story. This side story is clearly meant to draw in little kids and show a sympathetic side of Gamera.
The overall story is very obvious and the symbolism is extremely heavy-handed. The movie is like a treasure trove of kaiju cliches. Gamera is futilely attacked by the Japanese army. He crushes cities and countrysides like they are cheaply made miniatures. Science is the only thing that can really stop such a bully. And atomic energy is bad. The only cliche missing is a fight with other similar (but more villainous) kaiju. The film makers saved that for the sequels, according to the special features.
Even with its flaws, I enjoyed the movie, though that is mostly due to happy memories of watching it as a child and cheering for the monster who saves little boys. For others, it will most likely be a less endearing experience.
Mildly recommended, if you have a soft spot for turtles, heroic monsters, or happy memories of The 4:30 Movie showing stuff like this.