Story
When one space colony declared its independence from the Earth Federation, the devastating 7th Space War, an all-out war between Earth and space, resulted. The Federation responded to the Space Revolutionary Army with mobile suits, called Gundams. However, the Space Revolutionary forces played their trump card and dropped hundreds of space colonies onto the Earth, plunging the planet into a seven-year-long nuclear winter. The Federation collapsed, but the Space Revolutionary Army was unable to invade the Earth in the aftermath of the colony drop. Fifteen years have passed.
Synopsis via AniList (English).