The War of Blood refers to the underground conflict between the Sabbat under Mordred and the Black Hand under the Antediluvians. They fought a cold war between their agents from 2203 to 2255 while both were simultaneously hunted by Earth Federation Crusader Teams.
Gehenna caused the rise of the antediluvians, but many of them were eventually destroyed by the Tech Infantry. Those that survived retreated to the Wraithlands, cementing their control over those vampires that survived the apocolypse. Mordred, a fourth-generation vampire, had gone into hiding rather than serve the antediluvians. Meanwhile, his enemies solidified their control over the vampire community. In 2196, the Black Hand makes a deal with the Earth Federation to allow ghouls to join the Tech Infantry. In exchange, they take ownership of a system (later called Enoch) on the rim of known space. Two years later, when the Wraithlands become uninhabitable thanks to the Bug Asteroid that wiped out Earth, the antediluvians moved out and formed the Kingdom of Enoch.
Battle of Wilke's Star
With the Black Hand leadership on the Rim, Mordred made his move. Quickly gathering many vampire dissidents who opposed the antediluvians, Mordred reformed the Sabbat, and began challenging vampire controlled areas within the Earth Federation. This led to more defections, which caused Ventrue, the King of Enoch to declare Mordred a wanted criminal, and offer a high price for his heart. Ventrue also encouraged his allies in the Fed to hunt for Mordred as well, including the recently rescued Bruce von Eisenstein. In 2201, von Eisenstein found him and attempted to capture the wily vampire, only to be destroyed in turn. Mordred fled to Wilke's Star and formed a new headquarters there.