First battle of Ossus

In 21.9 BBY, one month after the First Battle of Geonosis and the beginning of the Clone Wars between the Galactic Republic and Confederacy of Independent Systems, a battle took place on the Outer Rim Territories planet Ossus between Republic and Separatist forces. Following an attack on the Republic world Bakura, Separatist forces advanced with the intent to take control of the Republic-aligned world. While also discussing battles at Bespin and Rhen Var, Jedi Master Mace Windu of the Jedi High Council stated to fellow Master Yoda that Ossus would fall within days. Ossus did eventually fall into Separatist control. The Galactic Federation of Free Alliances historian Voren Na'al mentioned the Separatist taking of Ossus in his historical archive, The New Essential Chronology, published sometime after 36 ABY.

The battle at Ossus was first mentioned in the 2002 video game Star Wars: The Clone Wars, developed by Pandemic Studios and produced by LucasArts as part of the Clone Wars multimedia project.