In the Star Trek fictional universe, the Klingon Civil War was the culmination of the power struggle between Gowron and the House of Duras, which continued even after Duras himself was killed at the hands of Lieutenant Worf in 2367.
The war began when Duras' sisters, Lursa and B'Etor, used Duras' illegitimate (and underage) son, Toral, to make a bid for the Klingon chancellorship. Captain Jean-Luc Picard, acting as arbitrator, refused to accept the bid as legitimate, at which point Toral and many Klingon members of the Council joined him in a war against Gowron.
The war proceeded with Worf and Kurn joining it on the side of Gowron, and was effectively ended when Lt. Commander Data prevented the Romulans from offering assistance to the forces of Lursa and B'Etor. The sisters escaped, but the life of captured Toral was spared at the insistence of Worf. Gowron eventually became chancellor of the Klingon Empire until his death in 2375.
The above events are seen in the episodes "Redemption, Part I" and "Redemption, Part II" of Star Trek: The Next Generation.
External link
The Klingon Civil War (http://www.memory-alpha.org/en/index.php/Klingon_Civil_War) at Memory Alpha, a Star Trek WikiWiki
Klingons (tlhIngan in the Klingon language) are a race of humanoids in the fictional Star Trek universe.
Shortly before the end of the Dominion War, in 2375, Gowron took direct control of the Klingon fleet (a position held up until that point by the successful General Martok) because he was concerned that Martok was becoming too popular among both the troops and the civilian population from his wartime success.
Conversely, Klingons despise the Tribbles as an "ecological menace".