So its happens after the event World War IV in 2807 that kills most of Earth's population and renders the planet uninhabitable, forcing everyone that survive to evacuate the planet.
Fifty-two years after the war, a research team from interstellar community called Galactic Federation is sent to Earth and discovers that the planet's heal itself. The Federation decides to repopulate the planet and sends over colonists. Cities and towns are eventually reformed over the next 20 years, but this also attracts attentions of criminals, military deserters, and other lawless scum who wanted to hide on Earth, away from authorities.
Fearing civil unrest caused by such ruckuss and the colonists forming their own government, the Federation gives the Strahl Democratic Republic (or SDR) the right to govern the planet in the late 2870s.
But, the usage of heavy-handed tactics such as uptight law and forced labour spark a massive reaction from the colonist, creating the Earth Independent Provisional Government as a declaration independence from the SDR. The SDR immediately establishes a puppet government and attempts to quell the uprising. The wealthy colonists hire mercenaries who are descendants of WWIV veterans to form the Independent Mercenary Army (or IMA), which is bolstered by the presence of SDR Foreign Legion defectors. They attack the SDR forces and the battle to control Earth begins in 2882.