Yoda, the ancient and revered Jedi Master, lived his final years hiding on the swamp planet of Dagobah. Nine hundred years old, Yoda had trained Jedi for eight centuries, and was very powerful in the Force. Among his last pupils were the most important (and reckless) Jedi in recent history, Obi-Wan Kenobi and Luke Skywalker.
In the waning days of the Republic, Yoda was a respected senior member of the Jedi Council. Serving alongside such luminaries as Mace Windu and Ki-Adi-Mundi, Yoda was present during the turbulent events that would eventually unravel the centuries-old Republic and seal the fate of the Jedi order.
Yoda served an important role in the Jedi Council. When young Padawans began their first foray into Jedi training, they did so under Yoda's guidance. Many of the Republic's greatest Jedi trained under Yoda when they were children -- schooled in groupings called clans. Once the Jedi hopefuls grew older, approaching their teenage years, they would then be paired to an elder Jedi Knight or Master to continue training one-on-one.
The pall of the dark side fell over the Republic during its twilight years, and Yoda grew increasingly concerned. The emergence of the dark side created a disturbance in the Force strong enough to cloud the Jedi's insights into important matters. Sensing the grave uncertainty of the future, Yoda recognized the need for answers. The Jedi Council dispatched Obi-Wan Kenobi to investigate an assassination attempt apparently carried out by Separatist forces. What he found was all the more troubling.