A conflict unfolded on Scrim Island amidst the Batonn insurgency, which was a smaller part of the extensive Batonn sector insurgency. Following the capture of the Imperial garrison situated on Scrim Island, a location on the planet Batonn, by the Batonn insurgents, Fleet Admiral Jok Donassius tasked Admiral Durril with its recapture. However, Donassius underestimated the cunning strategies employed by the Batonn rebels, resulting in substantial damage to his One Oh Third Task Force. Subsequently, Admiral Thrawn alongside Commander Eli Vanto infiltrated Batonn, successfully gathering intelligence regarding the tactics of the Scrim Island insurgents and their leader, Nevil Cygni. Leveraging this newly acquired information, Thrawn's 96th Task Force effectively dismantled the insurgents' defenses, compelling them to surrender.
During the Imperial Era, the Outer Rim planet of Batonn housed an Imperial garrison on Scrim Island. This island was located 300 kilometers to the west of Batonn's main continent. Batonn also featured several mines, notably the Creekpath Mining and Refining complex, which was situated close to Paeragosto City on the main continent. Leading up to 2 BBY, discontent with the governance of the Imperial Governor Restos spurred the rise of an insurgent movement across the planet, headed by Nevil Cygni. Utilizing his alias "Nightswan", Nevil had persistently attacked Imperial shipments of tibanna gas, iridium and doonium metals, as well as Wookiee slaves.
Nightswan encountered his adversary in the form of Admiral Thrawn, a rising Chiss star within the Imperial Navy. Having been repeatedly thwarted by Thrawn, Nightswan orchestrated the Battle of Scrim Island as a final attempt to eliminate the skilled tactician, whom he perceived as a threat to his scheme to overthrow the Empire. The Batonn insurgents successfully stormed and seized control of the Imperial garrison on Scrim Island, taking approximately one hundred hostages, including Imperial Navy troopers, technicians, and some civilian employees. Furthermore, they gained control of the island's deflector shield, coastal defenses, and three of its ion cannons. The insurgents also secured a turbolaser cannon.
Five days afterwards, Fleet Admiral Jok Donassius convened a meeting with Imperial admirals and governors operating within the Batonn sector. Following a briefing on the Scrim Island situation, he initially assigned Thrawn command of the mission. However, when Thrawn requested further study of the situation, Donassius, prioritizing the Empire's reputation, ordered the island's immediate capture or destruction. Thrawn voiced his disagreement, leading to the assignment of the Scrim Island operation to Admiral Durril and the One Oh Third Task Force. Thrawn's 96th Task Force was then redirected to pacify the Sammun insurgents.
Durril led the 103rd Task Force's attack on Batonn from the Imperial Star Destroyer Judicator. The Judicator, accompanied by its escort of Imperial light cruisers and frigates, initiated a bombardment of Scrim Island. However, they could not penetrate the deflector shield. Exploiting Durril's revealed capabilities, the insurgent commander on Scrim Island directed the ion cannons positioned on the western and southern coasts to target the Judicator. With the Judicator sustaining damage, Durril instructed his escort ships to retaliate by bombarding the western and southern ion cannons, but the insurgents reinforced their shield.
As the escort ships continued their futile assault, the ion cannon on the northern coastline struck the frigates and cruisers on the Judicator's portside flank, compromising their sensors and turbolaser targeting systems. Instead of adapting to the insurgents' tactics, Durril persisted with his ineffective attacks. While the northern ion cannon continued to bombard the escort ships, eight small freighters departed from the eastern edge of the shield, heading towards the main continent. Seven freighters maintained a low altitude to evade detection, while the eighth ascended into space. As Durril's task force remained immobilized due to ion damage, a turbolaser cannon situated north of the western ion cannon unleashed a barrage, striking the Judicator's starboard superstructure.
The Judicator absorbed three turbolaser salvos. The remaining four undamaged starboard escort ships targeted the weapon, but their shots were rendered ineffective when the insurgent commander reactivated the shields. Subsequently, the insurgent commander retracted the shields over the eastern shorelines as a ploy to lure the Imperials. As the Imperial ships redirected their fire towards the eastern shorelines, the western ion cannon struck, immobilizing them. With the escort ships incapacitated, the Scrim Island insurgent commander directed the turbolaser cannon towards the Judicator, inflicting damage upon its hull and weapons systems. The ion cannons then focused their fire on the weakened escort ships, preventing them from assisting the Judicator.
Unbeknownst to Durril and the Batonn insurgents, Thrawn and Commander Eli Vanto were observing the space battle. Exploiting a loophole in Donassius' orders, Thrawn deployed Commander Karyn Faro and the Ninety-Sixth Task Force to address the Sammun insurgents. He and Vanto then utilized the captured smuggler freighter Slipknot to approach Batonn and monitor the battle. Adopting the guise of a weapons smuggler, Vanto successfully secured coordinates for a meeting with the insurgent leader on Batonn. Thrawn also transmitted a distress signal on behalf of the 103rd Task Force. Thrawn also discreetly detached Captain [Brento]'s light cruiser Shyrack from the Ninety-Sixth Task Force and tasked the ship with tracking the movements of the seven freighters.
Eli and Thrawn piloted the Slipknot to the designated coordinates where the freighter was waiting. Adopting the alias "Horatio Figg", Vanto followed the freighter to a Nomad starship, a mobile ship-repair facility commonly used during the Clone Wars. Under Thrawn's guidance, Vanto donned an oversized Imperial officer's tunic to create the impression of a hardened gun dealer who had murdered an Imperial officer and stolen his uniform. Thrawn also equipped Vanto with a hold-out blaster designed to detonate when Vanto activated the title closest to the center of his chest. Thrawn remained aboard the Slipknot to orchestrate their escape.
Upon disembarking, Vanto was searched by three armed insurgents who confiscated his hold-out blaster, which aligned with Thrawn's plan. The insurgents escorted him to their leader, who identified himself as Nightswan. Nightswan recognized Vanto and informed the Imperial officer that he was aware of Thrawn's involvement. Nightswan asserted that the Empire was corrupt, dangerous, and ultimately self-destructive, and that his actions were aimed at bringing about its downfall. When Vanto disagreed, Nightswan retorted that the Empire lacked officers of Thrawn's caliber and revealed that he had orchestrated the Battle of Scrim Island to precipitate Thrawn's political demise.
Realizing that Nightswan was unaware that Thrawn was not in command of the 103rd Task Force, Vanto flattered his captor. Nightswan disclosed that a contact within the Thrugii asteroid belt had witnessed Thrawn with the Jedi General Anakin Skywalker during the Clone Wars. Meanwhile, Thrawn initiated a radiation leak within the Slipknot's engine compartment. Mistaking it for a typical Imperial trick, Nightswan instructed his men to override the ship's controls. Nightswan then questioned Eli about Thrawn's interest in his command abilities.
Before their conversation could continue, the Slipknot exploded. Thrawn had deliberately engineered the radiation leak to create a diversion facilitating their escape. He then ejected himself in the ship's escape pod. Recognizing this as Thrawn's signal, Eli detonated his hold-out blaster using his fake insignia plaque. Eli fought his way back to the hangar and escaped with Thrawn aboard one of the insurgents' freighters. Upon returning to the space surrounding Batonn, Thrawn and Vanto discovered that Bento had evacuated the battered 103rd Task Force, including the damaged Judicator.
After returning to Thrawn's Imperial Star Destroyer Chimaera, Thrawn participated in a hologram conference with Donassius and the other commanders. Despite Durril's failure, Admiral Kinshara and Commander Faro had successfully pacified the insurgents on Denash and Sammun. Donassius ordered the humiliated Durril to take the 103rd Task Force to the Marleyvane shipyards for repairs. After learning that Thrawn had obtained intelligence on the Batonn insurgents, Donassius tasked Thrawn with retaking Scrim Island.
Thrawn led the Galactic Empire's second assault on Scrim Island, commanding the Ninety-Sixth Task Force, which comprised the Chimaera, three light cruisers (Shyrack, Flensor, and Tumnor), and two frigates. Utilizing the intelligence gathered during their undercover mission, Thrawn formulated a strategy to break the siege of Scrim Island. To mislead the insurgents into underestimating his forces, Thrawn ordered the three light cruisers to descend into Batonn's atmosphere and bombard Scrim Island. While the ships exchanged fire with three ion cannons, their sensors and weapons were disabled by a fourth cannon.
Although the three cruisers had lost their primary weapons and main drives, their communications, secondary weapons, and auxiliary drives remained operational. Thrawn instructed the light cruisers to activate their auxiliary drives and reposition themselves. With the insurgents' fourth cannon malfunctioning, the Chimaera moved behind the three partially disabled cruisers and moved closer to the surface. This new position prevented the insurgent commander from targeting the Imperial ships with his ion cannons, but the Chimaera was still unable to target the ion cannons with its turbolasers. As the Imperial ships descended towards the surface, Thrawn ordered the Chimaera's turbolaser crew to bombard the waters surrounding Scrim Island, generating tsunamis that overwhelmed the insurgents' ion cannons and turbolaser emplacement.
The frigates relayed reports of the tsunami waves to Thrawn. Thrawn then demanded that the insurgents lower their shields and surrender. The Scrim Island commander accepted Thrawn's terms and lowered the shields. He and his men also complied with Thrawn's orders to leave their weapons in the building and await the arrival of assault boats. The Imperial hostages on Scrim Island were presumably freed. Thrawn also instructed Commander Faro to tractor the three light cruisers back into space to begin repairs. Vanto also reported the pacification of the Scrim Island insurgents to the galactic capital Coruscant.
While the Battle for Scrim Island had concluded, Thrawn cautioned that the "war for Batonn" was not yet over. Thrawn's prediction proved accurate. Nightswan had manipulated the events on Scrim Island to divert the Empire's attention while he regrouped his forces and weaponry at the Creekpath Mining and Refining complex, which was protected by a deflector shield. Although Nightswan had anticipated the Empire's withdrawal, Vanto had successfully traced the freighters' shipping vectors to the Creekpath facility. Consequently, Imperial forces and the allied Batonn Defense Force blockaded the complex, leading to the Siege of the Creekpath Mining and Refining complex.