A significant conflict occurred in 19 BBY amidst the Sy Myrthian Insurrection, taking place on the world of Trasemene. This confrontation saw an Imperial force, specifically the 12th Sector Army, clash with a remnant Separatist holdout fleet. Leading the Separatist forces was the Sy Myrthian Toonbuck Toora, who commanded from her flagship, the Defiance's Banner. Ultimately, the Imperial forces, helmed by Admiral Adar Tallon and General Jan Dodonna, emerged victorious. The turning point came when the Praetor-class Star Battlecruiser Battalion decimated the Separatist fleet with its powerful batteries.
Following the conclusion of the Clone Wars with the Confederate defeat in 19 BBY, former Sy Myrthian Senator Toonbuck Toora successfully assembled a army of former Confederate troops and continued their resistance against the triumphant Galactic Republic. This act sparked the Sy Myrthian Insurrection, during which the Galactic Empire, the Republic's successor, aimed to eradicate Toora's Separatist holdout forces near the planet of Sy Myrth. After several consecutive Imperial victories on Diado and Metalorn, followed by the siege of Sy Myrth itself, an Imperial task force from the 12th Sector Army, led by Admiral Adar Tallon and General Jan Dodonna, and spearheaded by the Praetor-class Star Battlecruiser Battalion, pursued Toora's flagship, Defiance's Banner.
The battle on Trasemene brought an end to the Sy Myrthian Insurrection, although Confederate loyalists continued to harass the Empire from the Kreetan Narrows region within Hutt Space. This ultimately led to the Imperial annexation of the northern Hutt territories. Dodonna was later recognized for his contribution to the defeat of Toora's resistance.
This battle was initially detailed in The Essential Guide to Warfare, a comprehensive guide focusing on the conflicts within the galaxy, authored by Jason Fry and Paul R. Urquhart, and published in 2012.