- See Civil War for more examples.
The Klingon Civil War was an internecine conflict fought within the Klingon Empire in late 2367 and early 2368. The war was waged between the supporters of the House of Duras and of Gowron, over who would be the rightful successor to K'mpec as Chancellor of the Klingon High Council. The forces backing Gowron were ultimately victorious, after it was revealed that the House of Duras was receiving backing and material support from the Romulan Star Empire. (TNG episodes: "Redemption", "Redemption, Part II")
Prelude to WarEdit
A time of great turmoil came to the Empire when Chancellor K'mpec died. He appointed an Arbiter of Succession which would be Captain Jean-Luc Picard of Starfleet, a Human, which was an unprecedented move in Klingon history. Picard decided between the two challengers who sought the leadership of the Empire, Duras and Gowron. It was eventually learned that Duras's father, Ja'rod, was responsible for the Massacre at Khitomer due to his alliance with the Romulans.
However, despite this, his position was strong among the Klingon High Council. Following Duras' death, his son Toral challenged Gowron for leadership of the empire. The Arbiter of Succession denied Toral's claim due to his age and concluded that Gowron would be the new Chancellor of the Klingon Empire. Despite this decision, half of the High Council sided with the House of Duras. This started the Klingon Civil War.
Closing days of the WarEdit
The war would rage on and would be uninterrupted by outside powers despite the fact that Gowron asked for Federation assistance which was denied because the Civil War was an internal conflict of the Klingon Empire. However, it was believed that the Romulan Star Empire was secretly supplying the House of Duras with weapons and supplies for the war in order to gain an ally against the Federation. This was subtly seen in the fact that the House of Duras remained strong despite the fact that their supply lines were destroyed.
Worf was captured by forces loyal to the House of Duras. Lursa and B'Etor attempted to seduce Worf into turning against Gowron, and giving up information about Starfleet. When Worf refused, he was taken by a Romulan guard, who then tortured Worf for information.
In order to expose the Romulan support, Captain Picard asked Chancellor Gowron to launch a full scale attack on the House of Duras in order for their leaders to ask for the Romulans for assistance. The Federation Council also approved of the plan to send a fleet to the Klingon-Romulan border under the command of Captain Picard of the USS Enterprise-D where it deployed a Tachyon sensor net which was designed to detect cloaked Romulan starships. The Romulans attempted to run the blockade and employed some trickery to evade the Starfleet vessels but were detected by Lieutenant Commander Data's vessel, the USS Sutherland. After being detected, the Romulan convoy abandoned its plan and returned to Romulan space and abandoned their allies.
The House of Duras base of operations would be assaulted by Gowron's forces ending the Civil War. A force led by Kurn stormed the facility, searching for Lursa and B'Etor, the Sisters of Duras. Lursa and B'Etor were able to transport out. Despite being seriously injured, Worf was able to overpower the Romulan guard, and was rescued by his brother. Toral was captured by Gowron's forces.
Following the end of the war, Captain Jean-Luc Picard and the USS Enterprise-D proceed to Qo'noS to give a full report to the Klingon High Council on the Romulan connections to the House of Duras. During this council session, Toral was brought into the chambers, and Worf was given the opportunity to execute Toral for the crimes of the House of Duras against the House of Mogh. Worf declined, and refused to allow Kurn to do so either. Worf explained that Toral had committed no crimes against Worf personally, and spared Toral's life. (TNG episode: "Redemption")
For the next several years the Duras sisters attempted to rebuild their forces in order to resume their fight against the Empire. The Duras sisters sold a quantity of bilitrium to the Bajoran Kohn-Ma terrorist Tahna Los. (DS9 episode: "Past Prologue") They later tried to raise funds by playing in the The First Annual Deep Space Nine Poker Tournament by cheating in the tournament. (DS9 novel: The Big Game) The Duras sisters allied themselves with Doctor Tolian Soran, and helped steal trilithium from the Romulans. Soran helped build a trilithium weapon capable of extinguishing a star, and agreed to provide the technology to the sisters in their attempt to gain control of the Klingon Empire. The sisters died in 2371 in combat with the USS Enterprise-D. (TNG movie, novelization & comic adaptation: Generations)
Toral was allowed to live. It is not clear if he was sentenced to discommendation following the defeat of the House of Duras. In 2372, he tried once again to conquer the Klingon Empire, by using information he was able to steal from Dahar Master Kor, by attempting to retrieve the Sword of Kahless from the Gamma Quadrant. Thankfully, Kor, Worf, and Jadzia Dax were able to prevent Toral's plan, and the Sword was later jettisoned into space. (DS9 episode: "The Sword of Kahless") Four years later, Toral and his supporters launched an attack against forces loyal to Chancellor Martok, when he claimed that he had control of the Sword of Kahless, and was the rightful ruler of the Empire. Because Worf had knowledge of where the real sword was hidden, Toral launched an attack upon him aboard the USS Avenger as it entered the Ikolis Expanse. Thankfully, Worf was able to escape and bring the real sword back to the Empire. Further probing proved that Toral was being supported by the Romulans, and Toral's insurrection was swiftly defeated. (TNG video game: Armada)
In an alternate timeline in which Doctor Noonien Soong's dream of widespread acceptance of artificial life in the form of Soong-type androids was realised, the House of Duras and its supporters won the civil war. This led to the reformation of the Klingon-Romulan Alliance, which worked against the United Federation of Planets. (TNG - Myriad Universes novel: Brave New World)