The Sabbat Civil Wars were a series of internal conflicts in the Sabbat. The sect has been wracked by three civil wars to date. With the final book of Vampire 20th anniversary edition -Beckett's Jyhad Diary- a fourth Sabbat Civil War has shaken the sect to its core.
Each of the Civil Wars has upset the Sabbat's power structure, and only the Black Hand remained unscathed through the original three conflicts. The recent death of Regent Melinda Galbraith left a power vacuum in the sect's leadership that ignited a fourth Civil War and formed the basis for the Gehenna Wars in Vampire 5th Edition .
First Sabbat Civil WarEdit
The First Sabbat Civil War began in North America around the time of the American Revolution. The conflict began as younger Lasombra and Tzimisce in the New World turned against one another in competition over mortal resources — resources that had became bitterly contested as more and more Cainites emigrated from Europe or sired new childer.
These younger Cainites had little supervision from their elders in Europe and little connection with the Sabbat outside the Americas; as a result, they had come over time to see their fellow Sabbat as competition rather than compatriots. The strife of this civil war allowed the Sabbat to lose much of their territory in the American East Coast to the Camarilla.
In a brief 30 years, the Sabbat's work had been undone by the very enemies they fled from in the Old World. 
The war ended with the signing of the Purchase Pact on September 19th, 1803, which declared all internal grievances void and forbade conflict amongst sect members. Further, it decreed that any Sabbat who waged open war against his fellows was to be hunted down and diablerized by his fellow Sabbat. 
Following this war, adherence to the Code of Milan became more widespread within the sect.
Second Sabbat Civil WarEdit
This war occurred in Mexico and Canada from 1863 to 1933. The conflict is generally said to have begun with the assassination of Regent Gorchist by Ravnos antitribu in Mexico City just prior to the French capture of Mexico City, likely in 1863. The conflict was exacerbated by rivalries between the Lasombra and Tzimisce that had been simmering since the prior Civil War; both Clans blamed the other for dominion of the United States slipping through the Sabbat's fingers. Fighting occurred primarily in Mexico, which was nearly torn apart as the Lasombra and Tzimisce swept up any clan, faction, or cult which could lend a strong arm.  Several would-be Regents emerged throughout the world even as the Sabbat south of the US border tore into each other with bloody relish. 
A combination of factors saw the internecine conflict end. The catalyst to the end of the war was the Shepherds of Caine hosting the apolitcal Conference of Caine in 1910 which brought many of the members of rival factions together under unspoken treaty.  Second, many packs turned to Melinda Galbraith, who had made Mexico City into a tenous neutral ground, for protection as the daytime battles of the Mexican Revolution caught them in its crossfire. With disease and warfare culling the herds the Sabbat depended on for sustenance, the fighting cooled. Galbraith took advantage of the situation and summoned the highest ranking envoys to Mexico City. With the support of several Packs plus the Seraphs of the Black Hand, presented herself as Regent and demanded the cessation of all hostilites.  While the conflict officially ended on December 21, 1933, when the Code of Milan was formally acknowledged by the sect and further revised into its current form at a conference in New York, in practice it ended with Galbraith's demand. 
Third Sabbat Civil WarEdit
This war occurred in the latter half of 1957, and lasted for only a hundred nights. The conflict began when Brujah antitribu in New York attempted a coup against the Lasombra and Tzimisce that had dominated the sect since its inception. After nearly two-thirds of the resident Sabbat in New York were killed in a conflict just shy of open warfare, the two sides agreed to settle the matter by diplomacy. The Lasombra and Tzimisce recognized their antitribu compatriots as equals within the sect and agreed to recognize the Clanless as their own unique distinction so the minority clans would have greater voice in Sabbat politics.  These Clanless demanded greater respect for their contributions and a greater share of glory. They fought against the staid beliefs and superstitions of archaic vampires, arguing that Clan had no meaning as to a vampire’s potential. In the end, they overcame many of the biases and bigotry within the Sect and earned a place for themselves as a Clan.  After a few months, they chose to name themselves "Panders" after the Caitiff "antitribu" Joseph Pander, who had killed the first Lasombra in the Third Sabbat Civil War. 
Fourth Sabbat Civil WarEdit
Following an explosion at the Gran Hotel Ciudad De Mexico, where the vampire archeologist Beckett was supposed to meet with the Regent-in-disguise , the Sabbat once more descend into a bloody internecine war. With a number of vampires in town due to the Palla Grande and three of the four Seraphs of the Black Hand vanished, the conflict has drawn in numerous vampires, even formally apolitical institutions like The Black Hand . This conflict is not localized, as Sabbat across the globe work themselves into apocolyptic frenzy certain Gehenna is at hand.
Other Sabbat question for the first time the nature of Gehenna. Many elect to defect to the Anarchs, with more fleeing in the span of five years than the previous four hundred. The ones that remain accept that the opening shots of a war that may last a hundred years have been fired, and these Sabbat will be the footsoldiers of the Gehenna Crusade to come. 
- VTM: Guide to the Sabbat (Revised), Page 17
- VTM: Guide to the Sabbat (Revised), Page 18
- VTM: Mexico City by Night, Pages 24-25
- VTM: Guide to the Sabbat (Revised), Page 19
- VTM: Mexico City by Night, Page 25
- VTM: Montreal by Night, Page 29
- VTM: Mexico City by Night, Pages 26-27
- VTM: Guide to the Sabbat (Revised), Page 19
- VTM: New York by Night, Page 26
- VTM: Rites of Blood, Page 51
- VTM: New York by Night, Page 27
- VTM: Beckett's Jyhad Diary, Page 148, 151
- VTM: Beckett's Jyhad Diary, Page 159