The SGI is the acronym given to the Soldiers of the Imperial Guard: the Special Operation Regiment of first Bazikstan, and then, the RFB: they are the dreadest and more effective human fighting force known to modern Aiers and to the Nebulosa of Ots.
The origin of the SGI is within the Imperial Guard of the Tork Empire of Cretor, being the Guard of the Sultan. After the Anglasecuarnian Wars, the Imperial Guard was disbanded, but some individuals of the former Imperial Guard will gather under the banner of Bazikstan, and will instaurate the Imperial Guard as an elite fighting force and regiment of Bazikstan.
While they where the harder fighters of Bazikstan in conventional Warfare, when the SGI will really earn it's fearsome reputation will be by the time of the Tris-Tigris-Hidraulic War for their covert and special operations operatives, being said that the strongest individual fighters of whole Aiers served in the ranks of the SGI.
Following this tradition, the RFB will replicate this in the Nebulosa of Ots, forming their RFB SGI around a core of SGI veterans of Bazikstan.