The Korriban-Ziost War was a conflict fought between the Sith of Korriban and Ziost and the human colonists of Ziost. Lasting five years, the conflict ended in the unconditional surrender of Ziost to the Sith, and the annexation of Ziost by the rising Sith League.
Following the fall of the Rakatan Empire, the Sith of Korriban, previously left divided by the death of their King, Adas, sought to capitalize upon the power vacuum left by the Rakata. Uniting under one banner, that of the Council of Kissai, the Sith began scouting surrounding systems in the hopes of reuniting their scattered colonist kin. The world of Ziost, close to Korriban and home to a large number of Sith colonists, was the first to be courted by the Korriban Sith, who dispatched a small diplomatic escort to Ziost to broker a peace.
Though negotiations were fruitful with the Ziost Sith, relations quickly soured with the non-Sith colonists of the world, the latter of whom feared Korriban's imperialist undertones and executed the Sith diplomats on the spot. This began a civil war between the Ziost Sith and non-Sith, into which the Korriban Sith waded a year later, invading the planet and reinforcing their brethren.
The Sith managed to launch successful campaigns on the continents of Kalmat and Greater Ronmar during the first years of the war, though the latter was temporarily reconquered by the Ziost humans following a several-month ceasefire in 5 AFRE. The continent changed hands frequently during 6 AFRE, and finally returned to Sith control during the last year of the war.
The united Sith emerged victorious over the human colonists in 7 AFRE, and the world was formally annexed into the newly-formed Sith League the same year.