The Blood River War was an ancient orcish war, of which not much is known. It was a savage conflict between the Dark Scar and a large tribe of Ogres. The conflict lasted for weeks, with each side making gains and losses, but an ambush by the Ogre Chieftain left the Dark Scar army crippled and desperate to make a final charge at the Ogre Encampment.
The great warrior Kash'drakor led the first and last push into the Ogre Camp himself with both armies collapsing and resulting in huge casualties, and the small tributary that divided the Orc and Ogre lands became flooded with blood, hence the name Blood River War. The few survivors fled into the wilderness, and for years afterward rogue Ogre tribes plagued the countryside, while most of the Orcs filtered back into the Horde.
The Dark Scar Clan was destroyed during this war. The only person known to have taken part in this war was Kash'drakor, who wielded the legendary axe Serathil. The last living descendant of Kash'drakor is Nazgrel, advisor of Thrall.