Though the Sith League greatly outnumbered and outgunned the Jedi Knights settled on the world, the Sith, despite their raw Force-awareness, suffered serious losses at the more practiced hands of the Jedi Knights, and it took the entire Sith League Military five years to eradicate the Jedi from the planet.
Though Ossus eventually proved to be a worthwhile investment for the growing Sith League, the conquest cost the League many lives, and combined with the ongoing Invasion of Felucia, stretched the League's military assets thinly across two fronts.
However, the dual wars forced the League to investigate other possibilities for the raising of armies. Soon after the war's start, the Ziost-based genetics research group, ZiGen, was awarded a contract by the League to investigate the possibility of cloning armies of enhanced Massassi warriors, which later came to serve as the mainstay of the Sith League Military.
The war eventually came to an end with the use of the tactic that won the Invasion of Felucia for the League. The Dwomutsiqsa-class carrier Midwan and a number of Derriphan-class destroyers bombarded the surface of the world from atmospheric orbit, reducing Jedi numbers significantly and securing the world for the League.