The assault known as the battle of Yrrna involved an attack on an Imperial storage complex situated within the Yrrna system.
Following the theft of an Imperial TIE Defender prototype and the kidnapping of the project's Chief Scientist with assistance from the renegade Grand Admiral Zaarin, the Crime lord of Nami, Ali Tarrak, acquired the capability to manufacture TIE Defenders. Seeking to disseminate this technology against the Empire, she orchestrated a demonstration for the Rebel Alliance by deploying TIE Defenders against a cargo depot in the Yrrna system.
Maarek Stele, considered the Empire's finest pilot, was sent to investigate the area in question.
Upon arrival, Stele, accompanied by his wingman, discovered that the surviving personnel had managed to board a Modular conveyor named Ulzepdi and were attempting to escape the devastation. They were being pursued by Tarrak's forces, who aimed to eliminate all witnesses. Stele engaged the first formation of T-wings from Gotmilc Squadron, but his wingman experienced a brief "malfunction". Subsequently, Stele and his wingman destroyed four Stormtrooper transports called Lucthz to protect the conveyor. Ultimately, two additional T-wing squadrons, Gotan Squadron and Notow Squadron, engaged Stele and his wingman, but both were annihilated. The Conveyor reached a safe distance and escaped the area into Hyperspace. With the cargo containers now destroyed, the TIE Defenders focused their attention on Stele and his wingman, who recognized their disadvantage in numbers and technological superiority and decided to retreat, encouraging Stele to do the same.
The assault realized the Empire's worst fears. They now possessed knowledge of Ali Tarrak's intentions through the crew and personnel aboard the Ulzepdi. Fortunately, Admiral Thrawn had engineered a new starfighter, the Missile Boat, to combat this grave threat and informed Emperor Palpatine of its completion. Palpatine promised Thrawn substantial rewards if these starfighters proved their worth by eliminating Zaarin. Thrawn promptly initiated testing of the Missile Boats.
This engagement is featured in the 1994 PC game Star Wars: TIE Fighter as the third mission within the New Threats campaign.