Based on their homeworld, Ruta III, the Rutan Empire once controlled the whole of the Mutter's Spiral. However, after engaging in their war with the Sontaran Empire, they were driven to the fringes of the galaxy.
In the early 1900s, the Rutan Army made a series of strategic withdrawals to specific strongholds, viewed by the Fourth Doctor as them losing the war. The Rutan Battlefleet at this time sent a scout to Earth, which was viewed by the Rutans as a strong point. However, the Doctor and Leela killed the scout and destroyed the approaching Rutan Mothership, convincing the Rutans that Earth's system was too dangerous to occupy. (TV: Horror of Fang Rock)