In 3680 BBY, during the second year of the Great Galactic War, a battle occurred between the reconstituted Sith Empire and Galactic Republic in the Seswenna sector of the Outer Rim Territories. This was the second battle in the Seswenna sector that the conflict had seen, and like the first, it was waged with the goal of breaking the Imperial blockade of the Rimma Trade Route—a super-hyperroute that ran through the region and supplied resources to the southern reaches of the Outer Rim. Unlike the first battle of the Seswenna sector, this effort proved to be successful, and the Republic Navy was able to regroup after their earlier defeat to overcome the forces of the Imperial Armada. The Sith were forced off of the Rimma Trade Route, which opened the hyperspace lane to usage by the Republic Military to resupply their fighting forces on Outer Rim fronts, like the contested Minos Cluster.
Republic soldiers taken as prisoners of war after the first battle of the Seswenna sector.
Early in the Great Galactic War, the Sith Empire launched a broad but strategic blitz against Galactic Republic interests and holdings in the Outer Rim Territories of the galaxy. After seizing the Tingel Arm and striking against tactically important worlds such as Korriban and Sluis Van, the Imperial Military launched a massive invasion of the resource-rich Minos Cluster. The offensive was initially very successful, in part because the Imperial Navy had positioned itself in the Seswenna sector along the Rimma Trade Route, effectively blockading the super hyperspace lane. The Imperial vessels held the Seswenna sector throughout 3681 BBY, successfully strangling Republic supply lines meant to carry reinforcements and materiel to Jedi defenders on the front lines of the Minos Cluster Campaign.
In 3680 BBY, a year into the war and blockade, the Republic Army mounted an effort to break the Sith control of the Seswenna sector. The counterattack was thoroughly unsuccessful and saw hundreds of Republic soldiers taken as prisoners of war by the Imperial victors. News of the defeat troubled the Jedi in the Minos Cluster and further lowered Republic morale. However, Republic Military leaders remained committed to breaking the Imperial fleet in the Seswenna sector to free up the vital Rimma Trade Route.
Shortly after the first attempt to break the blockade, the Republic's naval fleet, which had been scattered during the retreat from the Tingel Arm campaign, regrouped for a new assault against the Imperial Armada in the Seswenna sector. The gathered forces of the fleet moved against the blockade and successfully broke the Empire's hold on the Rimma Trade Route, winning the battle and securing the supply line.
News of the success was quickly spread to other battlefronts in the Outer Rim, raising morale and encouraging Jedi defenders to continue their fight. In the Minos Cluster, Jedi Knight Gnost-Dural, who was fighting on the front lines of the Battle of Eliad, was relieved to know that the end of the blockade meant the imminent arrival of reinforcements and supplies. As the war continued to drag on in later years, the Republic's ability to move forces along the Rimma Trade Route allowed for its armed forces and Jedi warriors to regain a foothold in the Minos Cluster, which was maintained until the end of the conflict in 3653 BBY. Mention of the battle was included in the wartime journal of Gnost-Dural, which was committed to the Jedi Archives on Tython during the Cold War.
The second battle of the Seswenna sector was first referenced in The Journal of Master Gnost-Dural, a 2011 book written by Robert Chestney under the in-universe persona of Jedi Master Gnost-Dural. The book was included as part of the Star Wars: The Old Republic collector's edition game bundle and served as a source of background lore to the massively-multiplayer online video game.