In the aftermath of Grand Admiral Thrawn's raid on the library planet of Obroa-skai during 9 ABY, a New Republic task force was dispatched in pursuit. This task force, led by an Elomin officer, eventually engaged Thrawn's forces near the Obroa-skai system. However, Thrawn exploited the psychological vulnerabilities of the Elomin commander, resulting in the destruction of the entire New Republic force due to Thrawn's superior tactical abilities.
The Chimaera, an Imperial-class Star Destroyer, awaited the return of scout ships that had been dispatched for the raid. Upon their arrival, Captain Gilad Pellaeon, the Chimaera's commanding officer, raised the sentry line to yellow alert following reports of being followed. Pellaeon then consulted with Grand Admiral Thrawn regarding their next course of action. Thrawn dismissed the scout wing commander's assertion that they had evaded their pursuers. Soon after, a New Republic pursuit force, consisting of four Assault Frigates and three wings of X-wing starfighters, materialized from hyperspace in a symmetric cloud-vee formation.
Instead of retreating or calling for reinforcements, as Pellaeon suggested, Thrawn opted to confront the incoming threat. As the scout ships hurried toward the Chimaera, Thrawn instructed three sentry line vessels to engage the approaching frigates. The Chiss Grand Admiral, observing the New Republic formation shift and eliminate one of the sentry ships, deduced that the opposing commander was Elomin and ordered the recall of the sentry line. To provide cover for the launch of its TIE/LN starfighters, the Chimaera's superstructure was oriented towards the pursuers. Subsequently, Thrawn directed the Sector Four sentry ships and TIE Fighters to execute a Marg Sabl closure maneuver.
Thrawn's understanding of Elomin art informed him that the New Republic commander would be psychologically unable to effectively counter the unpredictable attack pattern of the maneuver, given the apparent inferiority of the attacking forces. Consequently, the frigates and X-wings retreated into a defensive posture, allowing the Chimaera to seize the offensive. The result was the complete annihilation of the New Republic task force.