During the Imperial Era, the insurgent leader Nightswan led an insurgency against the Galactic Empire. Towards the end of his campaign, Nightswan shifted his operations to the Batonn sector with insurgent groups operating on the planets Batonn, Sammun, and Denash. The planet Sammun was governed by Governor Estorn, who answered to the Empire. Following the seizure of Scrim Island by the Batonn insurgents, Fleet Admiral Jok Donassius decided to take action against the sector insurgent groups including the Sammun insurgents.
After Admiral Thrawn insisted on studying the situation on Scrim Island, Admiral Durril was instead assigned to reclaim Scrim Island. Thrawn's 96th Task Force was instead assigned to pacify the Sammun insurgents. Deciding to investigate the Batonn insurgents, Admiral Thrawn and Commander Eli Vanto assigned Commander Karyn Faro to deal with the insurgents on Sammun.
Having studied Sammuni art, Thrawn instructed Commander Faro to enter the Sammun's system at a distance and disperse the rest of the task force. She was to bring the Imperial Star Destroyer Chimaera close to Sammun and demand the surrender of the insurgents. Imperial intelligence indicated that the insurgents were sheltering inside bunkers and were protected by deflector shields. However, these defenses could not withstand Star Destroyer turbolasers. In short, Thrawn's plan was to threaten at attack with the goal of driving them out of their positions.
Implementing Thrawn's plan, Commander Faro bombarded the Sammun insurgents' stronghold, forcing them to flee in starships. This plan worked and the Ninety-Sixth Task Force succeeded in destroying two enemy ships and capturing four others. In addition, the Empire captured a considerable array of small ordnance.
Following the pacification of the Sammun insurgents, Admiral Thrawn briefed Fleet Admiral Donassius and the other Imperial commanders about the successful operation. While Admiral Kinshara had success against the Denash insurgents, Admiral Durril's One Oh Third Task Force was repelled by the Batonn insurgents at Scrim Island with serious damage to the starships. As a result, Thrawn was assigned with ending the siege of Scrim Island. This enabled him to turn his attention to Nightswan and the remaining Batonn insurgents.
The Battle of Sammun was first mentioned in Timothy Zahn's 2017 novel Thrawn, a rebooted Canonical origins story of the titular character.