In 3680 BBY, during the early days of the Great Galactic War, a battle between the Sith Empire and Galactic Republic occurred in the Seswenna sector of the Outer Rim Territories. The battle was catalyzed by the Empire's naval blockade of the Rimma Trade Route, which had been strangling the flow of Republic military goods from the Core Worlds to embattled regions in the distant Outer Rim. Leaders of the Republic Military attempted to stage a counterattack in the Seswenna sector using the Republic Army, but the effort met with defeat. The victorious Sith took hundreds of Republic soldiers as prisoners of war in the aftermath and continued their domination of the Rimma Trade Route until later that year, when the Republic Navy regrouped in the Seswenna sector and launched a second offensive.
Sith and Jedi battle on Eliad in the Minos Cluster.
When the Sith Empire invaded the Galactic Republic in 3681 BBY, the two interstellar superpowers sparked the bloody Great Galactic War, which quickly spread across the galaxy and claimed many lives. In the early days of the war, the Republic Military struggled to organize effective defense strategies, allowing the Sith and their massive war machine to sweep across the Outer Rim Territories, seizing sector after sector. In the Tingel Arm, the Imperial Armada quickly secured newly conquered territory and planned a trap for the Republic Navy, which inevitably arrived in the region to retake its lost holdings. The Republic's fleet was quickly routed and scattered, throwing defense planning on the capital of Coruscant into disarray and allowing the Empire to make further advances in the Outer Rim. At this point, the Sith began targeting the Rimma Trade Route, a super hyperspace lane that ran from the Core Worlds of the Republic to the distant Outer Rim. At Sluis Van, a planet along the route, the Sith destroyed the Republic's shipyards and slaughtered many of the world's defenders. And at great detriment to the Republic, the Empire also invaded and claimed the resource-rich worlds of the Minos Cluster, which sat at the tail end of the Rimma Trade Route.
To further confound the Republic's defense efforts and claim a stronger hold on the Outer Rim, the Empire positioned elements of its naval armada in the Seswenna sector along the Rimma Trade Route, effectively blockading the lane to prevent the free flow of goods and war materiel. The blockade had a severe effect on the Jedi who had mobilized quickly in the wake of the Minos Cluster invasion and were now trapped on the battlefronts of the Outer Rim with waning supplies and little hope of reinforcement. For months, Jedi Knights on Eliad and other Minos worlds held out against the Imperial onslaught, but were unlikely to repel the invaders while the Rimma Trade Route remained closed.
In response to the blockade in 3680 BBY, leaders of the Republic Military devised a counterattack plan to strike against the Imperials in the Seswenna sector. The Republic Army engaged the Sith in the region, but was decisively defeated; the counterattack ended with no measure of success. During the battle, hundreds of Republic soldiers were captured by the Empire and taken as prisoners of war, bound in chains and herded into captivity.
The loss of the battle was a severe failure, particularly to the Republic forces fighting in the Minos Cluster. Reports of the captured Republic soldiers brought morale to a low point, as the Empire's treatment of previous prisoners of war indicated there was little hope that the incarcerated troops would be seen again. In spite of the setback, the Republic Navy managed to regroup its fleets and organize a second attack on the Imperial blockade in the Minos Cluster. That effort saw great success, with the Imperial Armada being forced to release the Rimma Trade Route by the end of the engagement.
The first battle of the Seswenna sector was introduced to Star Wars lore in the 2011 book, The Journal of Master Gnost-Dural. Penned by Robert Chestney under the persona of Jedi Master Gnost-Dural, the book is told through a series of journal entires that document the events of the Great Galactic War. The Journal of Master Gnost-Dural was included as part of the collectors edition bundle of Star Wars: The Old Republic, the massively-multiplayer online video game for which the book was written to provide background information.