In 2270, Keth's nephew Kang began consolidating his power and learning his future role as Emperor. Kang grew into another Klingon visionary, but in 2267 when he first encountered the Federation captain James T. Kirk, he was still caught in the Klingon web of distrust of the Federation that his uncle had helped weave. However, Kang's experiences on the USS Enterprise began the process by which he learned that the Federation was not his mortal enemy. Kang's ship encountered a distress call from a planet that he later learned was only a trap set by a creature that fed on hate. When he first arrived on the planet, he found Captain Kirk of the Enterprise and immediately blamed him for the loss of a Klingon colony that never existed. Kirk tricked Kang and had him put under guard on the Enterprise. When Kang's ship was about to blow up, Kirk saved what members of the crew that he could, even though they were all placed under guard on the Enterprise. Eventually, Kang and his crew escaped and began skirmishing in what could have turned into an interminable war with the Federation crew. Kang and Kirk finally discovered what was actually causing all the strange events and the trouble. After that, Kirk repatriated Kang and his crew. Upon his return to the Empire, Kang was relieved of his command for six months as punishment for being caught. Those six months gave him time to think about his uncle's view of the Federation and how it contrasted with what he saw on the Enterprise.
Upon her return to the Enterprise, Kang's consort Mara, who also was on the Enterprise, saw that the stories fed to the Klingon people about the Federation were untrue. She realized all of Kang's crew was well-treated aboard Kirk's ship. These events made her realize that there was no purpose served by the cold war with the Federation and she began to adamantly believe that immediate negotiations would be beneficial to both governments. She formed an underground movement on her homeworld, Pineli. She also bore Kang's son, Aethelnor, without Kang's knowledge and kept him hidden from the future-emperor for several years, eventually using him in a plan to get Kang to talk to the Federation.
In 2275 when the Klingons faced a blight and a severe famine, Kang kidnaped the Federation agent Jean Czerny. With her help and the hearty new Czerny strain of quadrotriticale, Kang solved the crisis and began to see the truth in the words of Kang the Seer. It was also at this time that he learned about his son. Aethelnor spent part of his early years in the Federation and this unique upbringing, straddled between the two superpowers, also contributed to the growing understanding between the two peoples.
Kang the Merciful, as he became known, was a student of Kang the Seer and of Kahless. Kang ascended to the throne in 2280 and chose gold and sliver for his crown. He chose these metals for many reasons, chief among them the fact that he was beginning to feel that different peoples could, in fact, work together and draw something from the differences between them. Under his rule an understanding of the Federation began to come about and many people began to see that the two did not have to be enemies. Unfortunately, even though many people agreed with Kang in his quest to end the cold war between the Empire and the Federation, many more saw their chances for power and glory in battle being lost. It was this group, a bastardized form of the former Klin Underground, that claimed responsibility for assassinating Kang in 2281. Once again, a violent Federation-hating brand of Klingon ruled the Empire. However, this time they were a mutation of the secret eugenics/radiation experiments conducted under Keth. They gave themselves the name Imperial Klingons and began, in 2282, a purge of all Klingons not of the Imperial race.