The Sumitra sector, alternatively known as the Tierfon sector, was a designated sector situated within the borders of the Expansion Region. Among the planets found in the Sumitra sector were Thustra, Boordii, Flax, Tierfon, and Alk'Lellish III. In total, this sector encompassed a substantial 12,387 planets and moons.
During the period of the Clone Wars, Thustra, a planet of significant influence, initiated actions to withdraw from the Galactic Republic. Jedi Master Yoda led Republic forces in an attempt to influence the decision of the planet's monarch, Alaric, but their efforts proved unsuccessful. His subsequent demise led to Thustra, and potentially the entire sector as foreseen by Supreme Chancellor Palpatine, falling under the control of the Confederacy of Independent Systems.
The Galactic Empire maintained a Tierfon Sector Fleet within the sector, while the Alliance to Restore the Republic operated the Tierfon Rebel Base on Tierfon throughout the Galactic Civil War. This base continued to function even into the early years of the New Republic. Following the Battle of Endor, the Sumitra sector was one of the initial regions to break free from Imperial rule.
According to The Rebel Alliance Sourcebook, Tierfon is located in the "Tierfon sector"; however, Heroes & Rogues, The Star Wars Sourcebook, and Star Wars: Rebellion place Tierfon within the Sumitra sector. Consequently, "Tierfon sector" is interpreted here as a common, informal name for the Sumitra sector.
The Sumitra sector was among the numerous sectors featured in Star Wars: Rebellion, which included ten planets within its boundaries; however, Rebellion contained several inaccuracies in its cartographic representations. Therefore, in instances where its placements contradict established canon placements, the canonical placements take precedence. Regarding the Sumitra sector, this applies to Kashyyyk, Qat Chrystac, Woostri, and Yavin Prime. Kashyyyk is actually located in the Mytaranor sector, Qat Chrystac is situated in the Parnabe sector, Woostri is found in the Woostri sector, and Yavin is within the Gordian Reach.