Sifo-Dyas was a human male Jedi Master who commissioned the Kaminoans' creation of the Grand Army of the Republic over a decade before the Clone Wars. A Jedi from the Cassandran Worlds, Sifo-Dyas was gifted with the power of foresight, and he earned a seat on the Jedi High Council prior to the Invasion of Naboo. When he foresaw a coming war that would ravage the galaxy, he believed that the Galactic Republic would require an army if it were to prevail. Yet, his peers on the Jedi Council rejected his notions, leading to his removal from the Council. Nevertheless, he pursued his ideas in secret and contacted the Kaminoan cloners, purporting to have the authorization of the Council and the Galactic Senate to raise an army for the Republic. In doing so, he unknowingly entered the crosshairs of the Sith, who set out to assume control of his cloning project.
Around the time of the Invasion of Naboo, Supreme Chancellor Finis Valorum requested Sifo-Dyas conduct clandestine negotiations with the Pyke Syndicate, and he headed for Oba Diah with Valorum's personal aide, Silman. However, the Sith Lord Darth Tyranus hired the Pykes to target Sifo-Dyas's T-6 shuttle, and they shot down his ship over the Oba Diah moon. Sifo-Dyas died in the resulting crash, but Silman survived and was taken prisoner by the Pykes. Consequently, Tyranus and his Sith Master, Darth Sidious, funded Sifo-Dyas's army of clone troopers, instructed the Kaminoan cloners to add Order 66 to the clones' inhibitor chips (which Sifo-Dyas originally intended to be a safeguard against any treacherous orders given to clones), and manipulated the Jedi Order into taking command of the army when the Clone Wars erupted. It was not until years later that the Jedi began to unravel the Sith's conspiracy and unearthed the details of Sifo-Dyas's demise.