- "This is the Imperial Star Destroyer Chimaera, calling the Overliege of Ukio. In the name of the Empire, I declare the Ukian system to be once again under the mandate of Imperial law and the protection of Imperial forces. You will lower your shields, recall all military units to their bases, and prepare for an orderly transfer of command."
- ―Thrawn's ultimatum to the Ukian Overliege
The Battle of Ukio was a brief battle in the Thrawn Crisis of 9 ABY where Imperial forces under Grand Admiral Thrawn tricked Ukio into surrendering by using cloaked cruisers to bombard the planet from under the surface in coordination with an orbital bombardment by the orbiting Imperial fleet.
Ukio was one of the five major producers of agricultural supplies for the New Republic and was ruled by the Ukian Overliege. The planet was defended by by a planetary shield. Following the Alliance's victory at the Battle of Endor in 4 ABY and the rise of the New Republic, Ukio was presumably one of the many worlds which had either seceded from the Empire or been liberated by Rebel forces.
In preparation for his attack on Ukio, the Grand Admiral had deployed some of his fleet including the Imperial-class Star Destroyers Bellicose, Judicator and Nemesis and Death's Head on diversionary attacks on Ando Prime, Filve, Crondre and Ord Pardron. This was to distract the already stretched New Republic forces who had already sustained losses at the battle for the lost Katana fleet. For the attack itself, Thrawn deployed two Star Destroyers including his flagship the Chimaera, ten of the Katana Dreadnaughts and an unknown number of cloaked cruisers. At his helm was the Dark Jedi Joruus C'baoth who would be responsible for coordinating the orbital bombardment of the cruisers via battle meditation.
- "The cruisers are ready, Grand Admiral Thrawn. As I am."
- ―Joruus C'baoth replying to Thrawn
As the Chimaera and its escort of Dreadnaughts descended on Ukio's surface at high orbit above the sunside equator, Thrawn demanded that the Ukian Overliege submit to the Empire by lowering its planetary shield and withdrawing its military forces to their bases to await Imperial occupation. When the Ukians delayed a response, Thrawn retaliated by ordering the Chimaera to fire its turbolaser batteries on the planetary shield. As expected, the planetary shield deflected the blasts. But under the influence of C'baoth's mind control technique, the two cloaked cruisers hovering beneath the shield at the two points fired upon by the Chimaera fired on the planetary surface in turn; obliterating two Ukian military air bases. Thanks to the near-instantaneous timing and the devastation sustained on the surface, the Ukians believed that Thrawn had developed a superweapon capable of blasting through planetary shield that could fit on a Star Destroyer.
- "Then you will be part of the Empire, will all the rights and duties that implies."
- ―Thrawn conversing with Tol dosLla
Rather than incur more destruction, the Ukian Overliege surrendered to Thrawn and subjected to his terms of surrender. These terms included lowering Ukio's planetary shield and allowing Imperial occupational forces to seize control of the shield generators and all ground-to-space artillery systems. All military vehicles larger than a command speeder were to be confiscated by the Imperial occupatiers. In exchange for accepting an Imperial military occupation, Thrawn also agreed not to interfere in the local political and social administration and to exempt Ukio from war-level taxation and military conscription. However, Thrawn also demanded that a significant proportion of Ukio's food production and processing facilities be diverted for the Imperial war effort. Rumor of this spread throughout the galaxy, although Talon Karrde, who had obtained a tape of the battle, later disproved this theory.