From Dragon Ball Encyclopedia, the ''Dragon Ball'' wiki
The Saiyan Army was first mentioned by Nappa when he stated that he was its highest ranking and most powerful General. The Saiyan Army appeared to be a faction within Freeza's Force. It was evidently destroyed when Freeza destroyed Planet Vegeta and killed the entire Saiyan race (minus four people, eight if the films are counted) along with it.
Factions and equipment
Main article: Saiyan-Tsufruian war
The Saiyan Army took part in only one known conflict before the Saiyans were annexed by Freeza in roughly 732 Age, and that was the Saiyan-Tuffle war, in which they were victorious. After a ten year long struggle, the Saiyans completely annihilated the Tuffles after a full moon arose, allowing them transformation into the Great Ape form. With the Tuffle race vanquished, the Saiyans completely colonized the planet, which they renamed Planet Vegeta after their commanding hero and King.
Occupation of Planet Vegeta
Main article: Occupation of Planet Vegeta
After the annexation by Freeza, the Saiyans were apparently automatically conscripted into Freeza's Force and seemingly all Saiyans physically and mentally capable were automatically drafted into the Saiyan Army. The Saiyan Army fought in hundreds of conflicts (if not more), and because of their high success record were given respect from Freeza.
The Saiyan Army forces even include babies, like Son Goku who was sent to Planet Earth twelve years prior to the beginning of the series to prepare the planet for Freeza's Force, but Goku lost sight of this after an accident left him permanently amnesiac. There were also Saiyan elites (one of them being Nappa).
While most of the known Saiyans have proudly served King Vegeta, Paragus was among the Saiyans who disagree with the king's naïve ways, namely because of his son, Broly, nearly being executed. Because the Saiyan Army leader's arrogance had Paragus and Broly nearly killed, Paragus plotted to avenge both himself and his son through the Saiyan prince, Vegeta.
As time went on, the fast growing power of the Saiyans began to frighten Freeza who believed that one day a Saiyan could be strong enough to challenge his might, and thus the final chapter in Saiyan history was written.
Genocide of the Saiyans
Main article: Genocide of the Saiyans
After Bardock and his band of low-class Saiyans soldiers (Toma, Shugesh, Borgos, and Selypa) ended the Kanassan war, something even Freeza's elites were unable to accomplish, the tyrant contemplated the destruction of the race. After Freeza's Spaceship approached the planet, King Vegeta and a squad of his strongest soldiers, staged an invasion of the spaceship to which Freeza retaliated by killing King Vegeta and his soldiers. Freeza then obliterated Bardock, Planet Vegeta, and the entire Saiyan race along with it by launching a Supernova at Planet Vegeta.
- King Vegeta