For the first fifteen minutes of "Chikyu Boeigun" (known in USA as "The Mysterians"), nothing happens. Scientist poking around a forest fire site comes face to face with a giant, metallic bird like monster. Then this film takes off, becoming more and more exciting. After the monster ravishes a village, the military kills it. We discover it's from the planet Mysteriod, and citizens of that planet are setting up a base here on Earth. The rest of the film concerns the battles betwen the Earth and The Mysterians. A bunch of Inoshira Honda's touches abound. There's a doomed hero (Ahikio Hirata) literally going on a kamikaze mission through the alien base, the plea for all nations to drop their petty squabbles and join forces to save the Earth, and wall to wall giant monster/spaceship excitement. Musician Akira Ifukube's score is militaristic, throbbing, and perfect. While "Gojira" is the best Japanese sci-fi classic, "The Mysterians", a candy coated treat is a close second, being the most fun.
Trivia note: Musician Akira Ifukube invented the famous Godzilla roar.