The Natarl's base for their invasion of Earth is located on the Moon.
In order to successfully take control of Earth's kaiju, the Kilaaks build a transmitter tower and a base on the Moon. The JSDF and UN launch an expedition force of humans aboard the Moonlight SY-3 to the Moon, and a battle rages which results in the humans blowing up the base's entrance, forcing the Kilaaks inside to revert to their metallic forms, and the destruction of the Transmitter Tower, freeing the Kaiju from the alien race's grip.
In the English dub's main song, "Save the Earth", it is mentioned in the lyrics that if the humans don't stop polluting Earth, the only option may be "movin' to the Moon".
According to Shinji Nishikawa: Drawing Book of Godzilla, an early plot for Godzilla vs. Megaguirus had astronauts finding Godzilla bones on the Moon. Shinji Nishikawa even prepared concept art for this plot, dated December 21, 1999.
To be added.
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