The Dreadnaught-class cruiser functioned as a warship within the Sith fleet belonging to the Brotherhood of Darkness near the conclusion of the New Sith Wars. In the year 1001 BBY, a trio of Dreadnaught cruisers was integrated into a Sith fleet that assaulted a Galactic Republic naval force positioned in orbit above the planet Ruusan. During this unexpected offensive, the Dreadnaughts utilized their laser cannons to target a pair of the Republic's Hammerhead-class cruisers that had compromised shielding; however, the Sith vessels were compelled to cease their advance when their targets deployed starfighter squadrons to counter them. Roughly one year later, the Sith employed Dreadnaught cruisers to establish a blockade around Ruusan, preventing a Jedi fleet from delivering reinforcements to support an active ground campaign on the planet. These Dreadnaughts would eventually engage the Jedi capital ships in space combat.
The Dreadnaught cruiser, which is homonymous with the capital ship type known as the dreadnaught, was a warship fitted with hyperdrive engines and armed with multiple forward-facing laser cannons.
Although they possessed less firepower, Dreadnaught cruisers could still represent a significant threat to the Galactic Republic's 315-meter–long Hammerhead-class cruisers once the latter's primary deflector shields were rendered inoperable. Conversely, a sufficient quantity of Republic starfighters could effectively discourage a Dreadnaught cruiser advance. Following their surprise attack on a Republic fleet, the Brotherhood of Darkness also deployed these ships to maintain a planetary blockade, with the intent of preventing a Jedi fleet from landing reinforcements.
In 1001 BBY, amidst the New Sith Wars, the Sith navy of the Brotherhood of Darkness commenced an attack against a Galactic Republic fleet that was stationed in orbit surrounding the Mid Rim planet Ruusan. The Sith contingent incorporated the Brotherhood's flagship, the Sith Destroyer Nightfall; a complement of three Dreadnaught cruisers; a pair of corsair battleships; and a number of interceptor and Buzzard starfighters. The Republic fleet, composed of four Hammerhead-class cruisers and three battleships, had a greater number of starships with superior firepower. Despite this, Dark Lord of the Sith Skere Kaan exploited the element of surprise to the Sith's advantage and coordinated the attacking force using the battle meditation Force technique.
The substantial Sith fleet—executing a perilous maneuver for a force of its magnitude—emerged from hyperspace collectively, initiating a bombardment of the Republic vessels even before they could issue an alert. When two of the Hammerhead cruisers suffered the loss of their primary shields after a strafing run by the Sith Buzzards, the Dreadnaught cruisers advanced to engage the suddenly vulnerable capital ships with devastating effect.
However, one of the Republic fleet's cruisers carried a Jedi Master who was also adept at employing battle meditation. Once the Jedi began applying the technique to the Republic's benefit, the Hammerhead cruisers targeted by the Dreadnaughts rapidly—and unexpectedly to Kaan—deployed four full squadrons of Aurek-class tactical strikefighters, which compelled the Sith vessels to cease their attack run due to the assault from the Republic fighters. Ultimately, the Sith were victorious in the battle, resulting in the total destruction of the Republic fleet.
Later, the Sith forces were drawn into a prolonged ground campaign on Ruusan against the Jedi Army of Light commanded by Lord Hoth. Subsequently, the Brotherhood of Darkness's navy established a planetary blockade to prevent a Jedi fleet assembled by Lord Valenthyne Farfalla from landing reinforcements to aid Hoth. The Sith fleet, under the command of Admiral Adrianna Nyras and nearly twice the size of the newly arrived Jedi naval force, included Dreadnaught cruisers and other vessels.
Because the Jedi fleet lacked the starfighters required to break the troop transports through the blockade, and given the strained relationship between Hoth and Farfalla, the force did not engage the Sith fleet, instead remaining outside the latter's targeting range. Approximately a year following the First Battle of Ruusan, Dark Lord of the Sith Darth Bane instructed the Brotherhood's fleet to engage the assembled Jedi force. The Dreadnaught cruisers targeted the Jedi capital ships, and several Jedi gunships exploited the opportunity created by the Sith fleet's broken formation to finally land on Ruusan. Shortly thereafter, the ensuing final battle on Ruusan led to the Jedi and the Republic emerging victorious in the overall war.
The Dreadnaught cruiser was first presented in the 2006 novel Darth Bane: Path of Destruction, written by Drew Karpyshyn as the initial installment in the Star Wars: Darth Bane Trilogy.
In "Cat and Mouse," the March 26, 2010 sixteenth episode of the Star Wars: The Clone Wars television series' second season, a data screen aboard the Galactic Republic Star Destroyer Resolute displayed tactical information pertaining to the Separatist dreadnaught Invincible. The data on the screen also featured, transliterated in the Aurebesh script, a segment from an article about the Dreadnaught cruiser sourced from the free, editable, and unofficial online Star Wars encyclopedia, Wookieepedia. When questioned about the canonicity of this excerpt and the information it contained, Lucasfilm Story Group member Matt Martin indicated that he considered it an Easter egg, thereby suggesting it was not canonical within either the current Star Wars canon or the franchise's Star Wars Legends continuity.