During his cadet cruise, Midshipman Vasak served onboard the IKS Gr'oth as an engineer during the incident at Deep Space Station K-7, when the engine room was swamped with tribbles transported from the Federation starship Enterprise. When Imperial Intelligence sought to lay blame on someone for the incident, they placed it at Vasak's feet, as he was an Imperial race Klingon and they were of the opinion that he should have known better. He received a permanent black mark in his record, but because of his connections in the Klingon High Council he was spared from execution and instead promoted - requiring a change of name to Kasak.
As his career progressed, Kasak achieved the rank of Captain and was given the task of commanding new vessels in their shakedown cruises, commands that would be terminated at the end - the vessels being given to someone more "politically sound". One of the vessels he tested was the IKV Hakkarl, the first of the K'tinga-class. He would be given the chance to test it once again, when it was refitted with automation technology that would allow the vessel to be controlled from the bridge of a B'rel-class bird-of-prey, the IKS Tazhat.
Upon receiving the orders to test Hakkarl/Tazhat, Kasak invested his personal fortune and connections to create a civil uprising on the planet Dekkanar, forcing the evacuation of Federation personnel. His plan was to somehow provoke the Federation into taking action against him as he arrived at Dekkanar, thus forcing the Organians to cede the planet to the Klingon Empire. To that end, he chose his entire crew - officers who had served with him before, and benefitted from his patronage - and took Hakkarl without authorization from drydock, then set a course for Dekkanar running on the pretext of a system malfunction (which had in fact happened on the journey from spacedock to Dekkanar).
What Kasak had not counted on was that one of the ships sent to expediate the Federation evacuation was the Enterprise, flying under the command of James T. Kirk - the man and the ship that had been responsible for the black mark in Kasak's record. At first attempting to deceive Kirk into thinking he was a defector, events ground into a confrontation between Enterprise and Hakkarl, in which the Klingon vessel - not requiring a crew, being remotely run from the bird-of-prey Tazhat - had the upper hand. It was the intervention of a Klingon squadron sent to intercept Hakkarl that turned the tide in Kirk's favor. With Hakkarl damaged and his crew turning against him, a mortally-wounded Kasak tied his free hand to his command chair and input his last order to the brain-damaged Hakkarl - to destroy Tazhat, and him with it. (TOS novel: Rules of Engagement)