I hope it's alright to bump a thread this old.
The way Atragon discusses Japan's wartime history really struck me the last time I watched it. It reminded me of what GMK would do decades later concerning Japan's past directing its future. It's quite the mashup of Godzilla's somber, thoughtful tone and the all-out invasion spectacle of The Mysterians, although in this instance the invaders are human. I'd quite like for the Mu empire to return someday in place of yet another alien invasion.
A lot of Godzilla fans are probably only aware of this film as the debut of Manda, but it doesn't have much to do... much like Maguma in Gorath. More than anything this is Jun Tazaki's movie as captain of the Gotengo - one of Toho's most iconic genre creations.