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"Should the Empire abandon theatrics, it could build a thousand small cannons for the cost of a single 'planet-killer.'"
―Haxen Delto, in a report to Airen Cracken referencing the Onager-class Star Destroyer[src]

The Onager-class Star Destroyer, also designated as the Onager-class Destroyer or Onager and nicknamed the Imperial Siege Breaker or Siege Breaker by members of the Rebel Alliance, was a type of rare capital ship and superweapon deployed by the Galactic Empire that was shrouded in secrecy. Initially developed to swiftly eradicate Separatist holdouts that remained after the Clone Wars and to bring Core Worlds under the control of the Empire, the Onager-class saw service throughout the Imperial Era. By the time after Death Star was active, the Onager was considered to be a possibly greater threat.

After the decisive Battle of Endor in 4 ABY saw the supposed death of Galactic Emperor Palpatine and the defeat of the Empire, the Onager was seen by the remains of the Empire as a vital instrument to regain power in the Galactic Civil War. There were several examples of this class which included the Cataclysm, the Rakehell, the Sunder, and the Onager-class Testbed. A notable characteristic of the Onager was its alleged kyber crystal-powered superweapons, which could either be Superheavy Composite Beam Turbolasers or Orbital Bombardment Particle Cannons. These weapons were powerful enough to engage capital ships from extremely long range, as well as conduct cataclysmic assaults on planets.

In the aftermath of the Galactic Civil War and the rise of the Empire's successor government, the First Order, it was believed by members of the Resistance, a private military force with roots to the Rebel Alliance and New Republic, that the First Order may have used technology or inspiration from the Onager. During the war between the First Order and the Resistance, the First Order Navy deployed the Mandator IV-class Siege Dreadnought which served with similar function as the Onager. The Mandator IV then served as inspiration for the Sith Eternal's Xyston-class Star Destroyers which were used when Emperor Palpatine sought to regain control of the galaxy.


General characteristicsEdit

"I'm just not convinced you need a moon-sized reactor to power a kyber crystal cannon."
―Haxen Delto, to Airen Cracken in a report[src]

The Onager-class Star Destroyer,[4] also known as the Onager-class Destroyer, the Onager, and referred to as the Imperial Siege Breaker[1] or simply the Siege Breaker by the Rebel Alliance,[2] was a type of cruiser-class Star Destroyer[1] capital ship[4] and superweapon[5] that was manufactured by Rothana Heavy Engineering under contract by Kuat Drive Yards and cost 376,500,000 credits.[1] Members of the Rebel Alliance believed that the Galactic Empire could build thousands of[2] Onager-class Star Destroyers[4] for the price of a single "planet-killer."[2]

It was propelled by five engine units in the stern of the starship, three of which were larger than the remaining two.[2] A solar ionization reactor was located in the ventral hull, characterized by its dome shape. The bridge was situated inside the elevated command tower at the center of the ship towards the rear, and the bridge itself was located on a near-trapezoidal structure on top of the command tower.[4] The Onager-class Star Destroyer was equipped with advanced targeting and extreme-ranged sensor arrays as well as a navigation computer. It featured a primary class 1.75 hyperdrive and a class 6 backup.[1]

The front of the ship was defined by two prongs which defined the bow as a T-shaped bow with a long indentation in the center that cut through to almost midship where the primary armament was located. Beyond the end of the indentation but before the command tower structure were two deflector shield generator domes similar to those[4][3] found in Imperial-class Star Destroyers,[7] as well as several other deflector shield generators.[1]

The deflector shields, however, were concentrated in the front of the vessel due to the ship's forward firepower being its unique characteristic.[5] More than half of deflector shields were concentrated towards the front of the vessel,[1] and as such, the aft and sides of the Onager-class were more exposed,[5] leaving the engines and flanks vulnerable. This trade-off was considered to be acceptable by the designers of the vessel.[1]

Also in the same fashion as ISDs,[8] the Onager-class had a ridge that traversed the port and starboard sides of the vessel. The Onager-class had two hangar bays, one located on the rear of each of the two prongs that form the T-shape of the bow.[4] Its complement consisted of six Lambda-class T-4a shuttles as well as thirty-six TIE line starfighters. The Onager-class was operated by 25,200 personnel which consisted of officers, pilots, and enlisted crew as well as holding 240 troops. The vessel also held 14,000 personnel for encumbrance and maintained consumables for one year.[1]


"Maybe I lack the Empire's taste for catastrophe?"
―Haxen Delto, to Airen Cracken in a report[src]
Onager firing

At one point, the Onager-class Testbed fired its Orbital Bombardment Particle Cannons on a terrestrial body.

Located in the indentation was the primary armament of the Onager-class, which were either two[4] shorter-ranged[5] Superheavy Composite Beam Turbolasers that were considered to operate as special battery armaments,[4] or two Orbital Bombardment Particle Cannons[5] that were classified as mass-driver cannons.[1] These weapons were speculated to be powered by kyber crystals by members of the Rebel Alliance, who believed the crystals were powerful enough to shatter mountains and anything but the strongest energy shield. Because of this, the rebels considered the ship to be a superweapon.[2]

The foundation of the weapons were at the end of the indentation by the bridge, and each weapon had at least three rings that were separated along the length of the indentation through which the payload of the weapons passed through. When these armaments fired, the indentation and rings glowed red or blue, and could fire almost simultaneously. These two Superheavy Composite Beam Turbolasers and Orbital Bombardment Particle Cannons were considered some of the Galactic Empire's most devastating weaponry and could be used to perform ignition attacks from beyond long range, allowing it to keep the crew of the vessel safe.[4]

Against fleets, the Superheavy Composite Beam Turbolasers focused on using auto-fire to burn through a lone target or sweep several targets as a cutting beam. If it used the Orbital Bombardment Particle Cannons, the Onager would attempt to shatter the most dangerous enemy vessel immediately.[1] These weapons in the indentation of the vessel were longer than half of the ship.[5] The primary armaments required an enormous amount of power, and the power conduits were susceptible to attack. The destruction of the main weaponry by a focused strike could cause a catastrophic failure to the systems of the ship, leaving it critically damaged or destroyed entirely.[1]

The Onager-class was also equipped with a number of ship-based weaponry throughout its hull ridges on its starboard and port sides, as well as near the hangars in the pronged sections of the ship.[5] These additional armaments were six twin heavy turbolaser batteries evenly divided to the port and starboard, twenty four heavy turbolaser batteries equally placed on the port and starboard, and twenty point-defense laser cannons evenly distributed to the forward, port, starboard, and aft of the vessel.[1]



An Onager-class Star Destroyer escorted by an Imperial-class Star Destroyer

The Onager-class Star Destroyer was shrouded in secrecy,[5] and was used by the Galactic Empire as a specialized orbital bombardment platform[4] deployed at long range that was originally conceived to ruthlessly end the deadlock of powerful planetary shields deployed by Separatist holdouts, revolutionary Core Worlds, and other dissident planets. When conducting orbital strikes, it targeted the shield generator and other ground-based defenses. As an uncommon ship, it was used for specific operations.[1]

It was also deployed against anti-fleet actions and in this regard, targeted the largest enemy vessels. It was usually accompanied by escort vessels to protect its flanks, and deployed its starfighters to defend its bow from critical strikes against enemy fighters.[1]

The Rebel Alliance believed that the Siege Breaker, if their intelligence was correct, acted in the capacity of a portable cannon.[2] The deployment of Onager-class Star Destroyers in more sensitive Imperial operations had the characteristic of not being able to be confirmed or denied,[4] and was unlike the common Victory-class and Imperial-class Star Destroyers.[5]

Since the Onager could destroy a base from orbit or punch through a cruiser, it was considered to be a valuable addition to fleets. Although the Death Star was one of the most visible symbols of the Empire's power, it was not their only superweapon, as the Onager-class was hidden in secrecy and may have been considered as an even greater threat.[5]


Early historyEdit

Following the Clone Wars, the Galactic Empire desired a warship that could efficiently and effectively shorten costly prolonged planetary sieges. As such, the Galactic Empire promptly developed the Onager-class Star Destroyer to ruthlessly engage planetary shields that were deployed by Separatist holdouts, rebellious Core Worlds, and other dissident planets that did not align with the Empire.[1]

Discovery by the Rebel AllianceEdit

"Passing on the latest from Maj. Harinar and Col. Delto. I've allowed their teams to operate independently, theorizing on the most likely configuration that a kyber superweapon would take. As you will see, they arrived at very different conclusions."
―Airen Cracken in a report to Mon Mothma[src]
Siege breaker

The Rebel Files included an illustration of what the Onager-class Star Destroyer may have looked like.

Sometime between the years[2] 5 BBY and 0 BBY[9] during the early rebellion against the Galactic Empire, after the Rebel Alliance began detecting hints of a kyber crystal-powered superweapon, Rebel Chief of Intelligence General Airen Cracken allowed Rebel Alliance Intelligence Service Major Capin Harinar of the Technology division and Colonel Haxen Delto of the Communications division to operate independently and theorize based on leads on the most likely configuration such a superweapon could take, and both arrived on different conclusions.[2]

Major Harinar gave a report to General Cracken on an Imperial project named Operation: Cinder. Colonel Delto, however, reported to Cracken on what was known as a Siege Breaker. His analysis led him to believe that the Empire could build thousands of relatively smaller cannons, which the Rebel Alliance dubbed Siege Breakers, for the cost of a single "planet-killer." The document also included possible speculation on the characteristics and armament of the Siege Breaker, an illustration of a Siege Breaker, and a comparison to a Jedi lightsaber as they both could cut through almost any material while remaining stable in a satchel.[2]

Delto used the document to pursue the principle that the Siege Breaker was more likely than the a large "planet-killing" battle station. After receiving both reports by Harinar and Delto, Cracken included them in his own report to Alliance Chancellor and Commander-in-Chief Mon Mothma. The report was later included in The Rebel Files, a central data repository that contained sensitive non-electric documents. Eventually, it was discovered that the "planet-killer" was the Death Star, a battle station that had the ability to destroy entire worlds.[2] At one point during the Imperial Era, an Imperial moff ordered an Onager-class Star Destroyer to destroy a city from orbit.[1]

Galactic Civil WarEdit


At one point during the Imperial Era, the Onager-class Star Destroyer Rakehell was accompanied by two Victories.

It was later discovered that the information gathered by Alliance Intelligence on Operation: Cinder[10] and the Siege Breaker[2] was correct,[10][2] including the illustration of the Siege Breaker[4] and of the Operation: Cinder satellites.[10] The Siege Breaker[2] was officially designated as the Onager-class Star Destroyer and was deployed by the Imperial Navy on various sensitive operations.[4]

Although a relative rarity, there were several examples of the Onager, with four being the Rakehell, the Cataclysm, the Sunder, and the Onager-class Testbed. Even during the Galactic Civil War[5] that took place from 0 BBY to 5 ABY,[11] the Onager-class Star Destroyer continued to be refined, and the Testbed allowed for the deployment of the Onager in its experimental variant.[5] The Rakehell at one point was accompanied by two Victory-class Star Destroyers while the Cataclysm was stationed near a pair of gravity wells and was receiving a Lambda-class T-4a shuttle and two TIE line starfighters.[4] The Sunder at one point participated in a battle against a Rebel Alliance MC80 Star Cruiser inside an asteroid field and sustained major damage. The Onager-class Testbed at some point fired its primary armament on a terrestrial body.[5]

The Onager-class Star Destroyer remained active after the decisive Battle of Endor that resulted in the destruction of the second Death Star and the death of Imperial Emperor Palpatine, and was still considered to be new and technologically advanced.[4] Despite the Rebel victory at Endor, the Onager-class Destroyer endured in secrecy.[5] Imperial forces that survived the Battle of Endor[4] in 4 ABY[12] made strides to strengthen their grip on the galaxy and launch a counter strike against the Rebel Alliance. The remains of the Empire believed that the Onager-class Star Destroyer was critical to achieving victory in the final stages of the Galactic Civil War.[4]


"Perhaps this is what the First Order is up to? Would represent a more containable risk."
―Caluan Ematt in a written annotation on The Rebel Files[src]

In 34 ABY[13] after the fall of the Galactic Empire, The Rebel Files were uncovered during an excavation on Durkteel and eventually reached the Resistance, a private military with roots to the Rebel Alliance and supported by some members of the New Republic. At that time, the Resistance was locked in a cold war with the First Order, the successor government of the Galactic Empire. Resistance Major Caluan Ematt reviewed the documentation related to the[2] Onager-class Star Destroyer[4] and left a written annotation describing that he believed that the First Order may have used technology or inspiration from the[2] Onager-class Star Destroyer,[4] and would represent a more containable risk.[2]

The concept of using heavy armament for orbital bombardments and long-ranged naval warfare was implemented into the First Order Navy's Mandator IV-class Siege Dreadnought, which functioned and was armed in a similar capacity,[14] and itself then served as inspiration for the Sith Eternal Xyston-class Star Destroyers which were instrumental in the reborn Emperor Palpatine's attempt to control the galaxy once again and reestablish the Sith Order.[15]

Behind the scenesEdit

The Onager-class Star Destroyer[4] was first mentioned and pictured in the canon boxset and reference book Star Wars: The Rebel Files which was originally released in November 21, 2017[16] and identified as the Siege Breaker. The book was authored by Daniel Wallace, and the image of the Siege Breaker was illustrated by Diogo Costa.[2] It was first identified as the Onager-class Star Destroyer in a news article by Fantasy Flight Games on its upcoming Star Wars: Armada expansion packs, Onager-class Star Destroyer Expansion Pack and Nadiri Starhawk Expansion Pack, which were released in late 2019.[4]

Lucasfilm Story Group executive Leland Chee confirmed that in developing the Onager-class for Star Wars: Armada, the design came first.[17] When asked how the design for the Onager-class came to be, Chee stated that the Onager-class was designed for The Rebel Files. When Fantasy Flight Games saw the design, it was further developed for their product as the design was appealing and fulfilled a gameplay need.[18]


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Notes and referencesEdit

  1. 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 1.10 1.11 1.12 1.13 1.14 1.15 1.16 1.17 1.18 1.19 1.20 1.21 1.22 1.23 1.24 1.25 1.26 1.27 1.28 1.29 1.30 1.31 1.32 1.33 1.34 1.35 1.36 Starships and Speeders
  2. 2.00 2.01 2.02 2.03 2.04 2.05 2.06 2.07 2.08 2.09 2.10 2.11 2.12 2.13 2.14 2.15 2.16 2.17 2.18 2.19 2.20 Star Wars: The Rebel Files
  3. 3.0 3.1 3.2 Topps logo Star Wars: Card Trader (Card: Star Destroyer - Blueprints) depicts an Imperial-class Star Destroyer, and identifies deflector shield generator domes and a solar ionization reactor. Armada Star Wars: Armada – Onager-class Star Destroyer Expansion Pack depicts an Onager-class Star Destroyer with those same objects. Therefore, it can be deduced that the Onager-class was equipped with deflector shield generator domes and a solar ionization reactor.
  4. 4.00 4.01 4.02 4.03 4.04 4.05 4.06 4.07 4.08 4.09 4.10 4.11 4.12 4.13 4.14 4.15 4.16 4.17 4.18 4.19 4.20 4.21 4.22 4.23 4.24 FFG A New Age of Battle on Fantasy Flight Games' official website (backup link)
  5. 5.00 5.01 5.02 5.03 5.04 5.05 5.06 5.07 5.08 5.09 5.10 5.11 5.12 5.13 5.14 FFG The Siege Breaker on Fantasy Flight Games' official website (backup link)
  6. Star Wars: The Rebel Files establishes that 14 AFE and 19 AFE in the Imperial calendar are respectively 14 and 19 years after the Proclamation of the New Order. Given that Star Wars: Galactic Atlas dates the Proclamation to 19 BBY, 14 AFE must therefore correspond to 5 BBY, while 19 AFE corresponds to 0 BBY. The content of Star Wars: The Rebel Files is chronological, and the information pertaining to the Onager-class Star Destroyer corresponds to the time between 5 BBY and 0 BBY. As such, the Onager-class must have been introduced during or prior to 0 BBY. Starships and Speeders establishes that the Onager-class was developed shortly after the end of the Clone Wars. Star Wars: Episode III Revenge of the Sith depicts the end of the war, with Star Wars: The Galactic Atlas placing the events of the film in 19 BBY. Therefore, the Onager-class must have been developed between 19 BBY and 0 BBY.
  7. Topps logo Star Wars: Card Trader (Card: Star Destroyer - Blueprints)
  8. Rogue One: A Star Wars Story
  9. Star Wars: The Rebel Files establishes that 14 AFE and 19 AFE in the Imperial calendar are respectively 14 and 19 years after the Proclamation of the New Order. Given that Star Wars: Galactic Atlas dates the Proclamation to 19 BBY, 14 AFE must therefore correspond to 5 BBY, while 19 AFE corresponds to 0 BBY.
  10. 10.0 10.1 10.2 Star Wars Battlefront II
  11. Star Wars: Galactic Atlas establishes that the Battle of Scarif and the Battle of Jakku date to 0 BBY and 5 ABY, respectively. Rogue One: A Star Wars Story establishes that the Battle of Scarif was the commencement of the Galactic Civil War, while Aftermath: Empire's End establishes that the Battle of Jakku marked the official end. Therefore, it can be deduced that the Galactic Civil War took place from 0 BBY to 5 ABY.
  12. Star Wars: Galactic Atlas establishes that the Battle of Endor took place in 4 ABY.
  13. Star Wars: The Rebel Files establishes that The Rebel Files were buried on the same day as the Battle of Endor, which takes place in 4 ABY, according to Star Wars: Galactic Atlas. Since Star Wars: The Rebel Files also establishes that the files were rediscovered thirty years later, they must have been uncovered in 34 ABY.
  14. Star Wars: Episode VIII The Last Jedi
  15. Star Wars: The Rise of Skywalker: The Visual Dictionary
  16. Canfield, David (2017-11-21, 5:00 pm). Star Wars: The Rebel Files book trailer unlocks secrets of the Rebel Alliance. Entertainment Weekly. Meredith Corporation. Archived from the original on July 25, 2018. Retrieved on July 29, 2018.
  17. TwitterLogo Leland Chee (@HolocronKeeper) on Twitter "It's been quite a long time coming but at last we reveal the look of the Nadiri Starhawk introduced in the Aftermath books. With the Onager, the design came first." (backup link) (screenshot)
  18. TwitterLogo Leland Chee (@HolocronKeeper) on Twitter "Rebel Files came first. FFG liked the design and it fulfilled a gameplay need." (backup link) (screenshot)

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