Sagittarius is one of the largest ships that humanity has ever developed. originally the Super-carrier was going to be used as a Mobile headquarters for a branch of the Sanctrian Government. however the Nazars launched a mass invasion force in the Frigaria system. The Sagittarius was the first one to respond where it held out several waves of Nazar fleets before the Sendra and Terrain where able to jump in the frenzy.
The Sagittarius was transformed into a carrier, the largest of its kind. however the primary problem lied in the desins that there were no fighters that the Sagittarius could carry. this is when the River class Fighter was born, welding 8 gun ports, the small fighter could take out a few nazar interceptors and even a medium warships if the pilot is good enough.