By 2154, K'Vagh was a General in the Klingon Defense Force stationed on Qu'Vat colony. That year, scientists under orders from the Klingon High Council led by Doctor Antaak began efforts to create genetically enhanced soldiers using human Augment DNA. Soldiers under K'Vagh's command, including Lieutenant Laneth and his own son Marab were injected with a strain of Qu'Vat virus that infused them with Augment DNA. This gave them enhanced abilities but caused their appearance to change.
The virus soon got out of control, and began spreading not only throughout the colony but the wider Klingon Empire as well. Dr. Phlox was kidnapped on Earth and brought to Qu'Vat to work on stabilizing the virus. Phlox was able to cure the virus, but not before K'Vagh and several hundred million other Klingons had been changed by the virus into more human-like Klingons, which were called QuchHa' Klingons.
Meanwhile, K'Vagh's subordinate Laneth admitted feeling fear for the first time since she was a child. She worried that there would be no place for them in the Empire, but K'Vagh swore that as long as he was alive, he would ensure the place of the QuchHa' in the Empire. (ENT episode: "Divergence")
By 2165, K'Vagh and fellow General Kor, son of Kaltar were leading a resistance against unaffected Klingons, who were called the HemQuch. Laneth remained under K'Vagh's command, and was a Captain by that time. Marab however had died in battle against the HemQuch prior to mid-2165. Many unaffected Klingons were determined to exterminate the QuchHa'. Working with the Klingon pirate Lokog, the rebels attempted to defeat the HemQuch with Ware technology, however the HemQuch discovered how to permanently destroy the Ware.
The rebel forces battled to hold their territory. In November 2165, Laneth, K'Vagh, and Kor were invited by the new Chancellor Khorkal to parlay in the Klingon High Council chambers. During that meeting, Khorkal ordered a duel to resolve the issues with the QuchHa'. Injured in battle against the HemQuch, K'Vagh was allowed to have a Cha'DIch fight for him. Laneth volunteered to fight for General K'Vagh against Councillor B'orel, who was leading the HemQuch persecution of the QuchHa'.
B'orel for his part arrogantly assumed that Laneth would be an easy kill, however he was quite mistaken. Laneth was able to easily provoke the young hotheaded councillor into making several fatal mistakes and killed B'orel in combat. As B'orel died, K'Vagh opened B'orel's eyes and performed the Klingon death ritual. Because Laneth won the duel, Khorkal allowed the QuchHa' to exist in the Klingon Empire, with noble QuchHa' allowed to retain their land and titles without further challenge. K'Vagh was allowed to take B'orel's place on the High Council, becoming the voice of the QuchHa' on the council. (ENT - Rise of the Federation novel: Live by the Code)