Genocide of the Saiyans is the name given to the very brief but incredibly disastrous conflict between Frieza's forces and the Saiyan race. It should be noted that "Genocide of the Saiyans" isn't an official term, but commonly used.
Main article: Dragon Ball Z: Bardock - The Father of Goku
After receiving word from Zarbon that a band of low-class Saiyans had successfully conquered Planet Kanassa, a mission stated by Dodoria to be so difficult that even elite squadrons of soldiers had not even bothered attempting it, Frieza was in utter disbelief. Initially, Frieza realized that no Saiyan alive at the time would be any sort of threat to him or his vast empire, but contemplated on the fact that the Saiyans power was quickly growing, and sometime in the near future, a Saiyan warrior may arise that could possibly challenge his might, especially if the Super Saiyan legend was evidently true. Frieza soon ordered the Saiyan squad responsible for the Kanassan war victory to be given another assignment, one that would be used as a distraction for a deadly ambush.