The Chiss Ascendancy endured an assault on Csilla, a conflict that pitted its forces against a trio of attacking warships. These unidentified vessels belonged to the Paataatus Hiveborn, although their identity was unknown at the time. The Nikardun Destiny, their conquerors, had instructed the Hiveborn to target the Chiss homeworld and capital of Csilla. This strategic move aimed to divert attention from a Nikardun massacre of refugees occurring at the Dioya system, situated on the Ascendancy's periphery. Ultimately, the Grysk Hegemony, seeking to encircle, undermine, and ultimately invade the Chiss Ascendancy, orchestrated the Nikardun's conquest of the Paataatus and other neighboring nations.
The Chiss Defense Force swiftly repelled the attackers. However, the timing of the assault, coinciding with a legislative session of the Chiss Syndicure, ignited turmoil among the Ascendancy's ruling Aristocra. The Syndics became fixated on identifying and punishing the perpetrators, as an attack on Csilla was unprecedented in recent history. Supreme General Ba'kif of the Chiss Expansionary Defense Fleet, however, prioritized understanding the motivation behind the attack over simply identifying the attackers. Despite his reservations, Ba'kif authorized a retaliatory strike against the Paataatus homeworld as punishment for recent raids against the Ascendancy.
The Grysk Hegemony, an expansionist power governed by the bellicose Grysk species, had ambitions to conquer the Unknown Regions, referred to locally as "the Chaos." The Grysk operative "Jixtus" had manipulated Nikardun general Yiv, known as "the benevolent," to spearhead the Nikardun Destiny in conquering the nations nearby and surrounding the Chiss Ascendancy. Jixtus devised a plan for the Ascendancy's demise. Ascendancy military doctrine prohibited military action against entities that had not directly attacked the Chiss, even if they posed an imminent threat. Consequently, a nation could conquer the Ascendancy's neighbors in preparation for an invasion without facing legal repercussions from the Chiss Expansionary Defense Fleet. Jixtus envisioned the Nikardun's encirclement of Chiss territory as the initial step towards a successful invasion.
Among the nations bordering the Ascendancy were the Paataatus, a species whose government frequently launched raids into Chiss border systems. Around 19 BBY, Jixtus orchestrated Yiv's conquest of the Paataatus. Simultaneously, Jixtus deployed agents of the telepathic Agbui species to instigate a civil war on the planet Sunrise. This conflict devastated the native population, and the survivors were subsequently enslaved by the Grysks to mine nyix, a precious metal used to reinforce the hulls of warships. However, a group of refugees led by the Magys fled Sunrise to the Rapacc system, where they established a colony among the native Paccosh. Haplif, the leader of Jixtus's Agbui saboteurs, contacted Nikardun forces to eliminate the Magys' refugees. Consequently, the Nikardun conquered and blockaded Rapacc. Nevertheless, the Paccosh managed to dispatch two refugee starships towards the Chiss Ascendancy, seeking assistance against the Nikardun.
Around 19 BBY, one of these Paccian refugee ships reached the Ascendancy's outlying Dioya system, where the Nikardun massacred them. Yiv then commanded the Paataatus to attack the Ascendancy's capital planet of Csilla to divert the Chiss from the massacre.
Appearing from disparate hyperspace vectors above the Chiss homeworld and capital of Csilla, three Paataatus warships immediately launched an attack on the Chiss defense platforms stationed above the planet, utilizing their spectrum lasers. Within a single minute, the Chiss Defense Force responded with counter-fire. The attacking warships proceeded to bombard the Chiss capital city of Csaplar with missiles, but the defense platforms successfully intercepted them in orbit, minimizing surface damage. The Chiss warships effectively destroyed the invading vessels within fifteen minutes of the attack's initiation.
The assault unfolded while the Chiss Syndicure was actively in session. Consequently, the majority of the Ascendancy's high-ranking Aristocra were assembled at Csaplar's Assembly Cupola for important governmental proceedings. The attack instilled sufficient fear within the Syndicure, leading them to request reinforcements from the Chiss Expansionary Defense Fleet stationed at Csilla and other core Chiss territories. This came at the expense of withdrawing forces from the Ascendancy's border regions. In fact, weakening the Ascendancy's periphery was a primary objective of the unknown adversary behind the attack.
The true instigator of the attack was General Yiv and his Nikardun Destiny, who orchestrated the assault to conceal the attack on the edge of the Dioya system. Supreme General Ba'kif recognized this diversionary tactic. However, the Ascendancy attributed blame to the Paataatus government, the force utilized by the Destiny to avoid deploying their own vessels. This misattribution resulted in a Chiss retaliation in the form of the attack on the Paataatus. Nevertheless, Thrawn persisted in his investigation to uncover the true masterminds, ultimately revealing the Nikardun as the genuine threat.
Following the battle, Supreme General Ba'kif dispatched Senior Captain Mitth'raw'nuruodo, known as "Thrawn," who was recovering from injuries sustained during Vagaari pirate operations at a medcenter on Naporar, to investigate the event the attack on Csilla was meant to distract the Ascendancy from discovering.
Thrawn's analysis of the attack recordings led him to conclude that the warships involved were antiquated and even "slightly obsolete." Consequently, Thrawn informed Ba'kif that he believed the ships would not resemble the current vessels employed by the true enemy.
The attack on Csilla serves as the opening event of the 2020 novel Thrawn Ascendancy: Chaos Rising, the first book in Timothy Zahn's Ascendancy Trilogy. The investigation into the attack serves as a catalyst for General Ba'kif and Senior Captain Thrawn to uncover the threats that form the central conflict of the novel.