"I am Koloth."
"That doesn't answer my question."
"Yes, it does."
Koloth was among the most legendary warriors, heroic military leaders and adept negotiators in the Klingon Empire during the late 23rd and early 24th centuries. He was known in the United Federation of Planets chiefly for his encounters with Captain James T. Kirk and Curzon Dax, and for his long friendship with fellow Klingon officers Kor and Kang.
As a product of 22nd century genetic engineering, Koloth was descended from Klingons afflicted with the Augment virus created in 2154. By the 24th century, he seemed to have been cured or cosmetically altered. (ENT: "Divergence"; TOS: "The Trouble with Tribbles"; DS9: "Blood Oath", "Trials and Tribble-ations") He also had a son. (DS9: "Blood Oath")
Koloth's status within the Empire was revered to the extent that he achieved the status of a Klingon Dahar Master. His glory further succeeded him, after his death in 2370, when he earned his own statue among the Hall of Heroes on Qo'noS. (DS9: "Blood Oath", "The Sword of Kahless")
Much of Koloth's early career is unknown. However, by the 2260s, he had achieved the rank of captain and was assigned as commander of D7-class battle cruiser IKS Gr'oth. (DS9: "Trials and Tribble-ations")
In 2268, the Gr'oth was on a six-month mission, assigned to patrol the border of the Klingon Neutral Zone. Around stardate 4523.3, Koloth ordered the Gr'oth to stop at the Federation Deep Space Station K-7 to claim shore leave rights. Shore leave was accepted, but shortly thereafter, a brawl between his crew – precipitated by his first officer, Korax – and a group of Starfleet officers from the USS Enterprise, then commanded by Captain Kirk, broke out on the station. Koloth demanded that Kirk issue a formal apology and assume full responsibility for the "persecution" of Klingon nationals in the quadrant. Kirk refused, citing a recently discovered Klingon plot to poison a shipment of grain destined for Sherman's Planet. (TOS: "The Trouble with Tribbles"; DS9: "Trials and Tribble-ations")
In 2269, Koloth captained the IKS Devisor while he pursued a Federation scout ship piloted by Cyrano Jones, a Federation citizen who was responsible for causing ecological sabotage to a Klingon planet and stealing a Klingon glommer. Koloth encountered and attacked the USS Enterprise, under Kirk's command, in order to retrieve Jones and the glommer. (TAS: "More Tribbles, More Troubles")
Koloth, Kor, and Kang, who originally set out with forty legions, together held the Korma Pass against T'nag's army in a glorious battle in a trinary star system. The three warriors forced the enemy to fight with the blinding light of three suns in their eyes. The battle ended with the mountainside covered with so many dead that there was not a square meter of ground to be seen. They together feasted on T'nag's heart, in celebration of their victory. (DS9: "The Sword of Kahless", "Once More Unto the Breach")
In 2289, Koloth represented the Klingon Empire in negotiations at the Korvat colony with the Federation. Koloth had little use for the Federation, and his implacable demeanor towards their top ambassador, Curzon Dax, earned him the nickname d'akturak or "ice-man". No matter how reasonable the proposal or how much it favored the Klingon Empire, Koloth was never satisfied. (DS9: "Blood Oath")
During the late 2280s, a band of depredators, led by the Albino, began raiding Klingon colonies. Three Klingon warships, led by Kor, Koloth, and Kang, were sent out to stop him. Their mission was successful in capturing most of the depredators, but the Albino was able to escape. In the Albino's last message to the Klingons, he promised to take his revenge on the firstborn of each of the three captains. Within a few years, he kept his word and managed to infect the warriors' three innocent children with a genetic virus that eventually killed them. (DS9: "Blood Oath")
The blood oath
In 2290, Kor, Kang, Koloth, and Curzon Dax pledged a blood oath to avenge the deaths of the sons of the three Klingon captains, the offense committed by the Albino. They nearly caught him at Galdonterre, but one of their subspace messages was intercepted and he once again was able to escape.
After decades of searching, Kang learned in 2370 that the Albino was on the planet Secarus IV. Kang traveled there and discovered his compound. The Albino knew immediately of his arrival and invited the trio to a "fair fight" and one last glorious battle. Kang contacted both Kor and Koloth for a rendezvous on Deep Space 9, in preparation of their final attempt to complete their long quest.
Three months later, Kor, Koloth, and Kang, with the aid of Jadzia Dax, prepared their attack on the Albino's compound, only to discover that it was a trap. Using the element of surprise, they bombarded the compound with tetryon particles, forcing the Albino and his sentries into face-to-face, hand-to-hand combat. Koloth was fatally wounded, fighting the Albino's personal guard. Following a fierce duel, Kang was able to slay the Albino (held at bay by Dax), before he died as well. Having fulfilled their blood oath, both Kang and Koloth died glorious and honorable deaths. (DS9: "Blood Oath")
Originally Koloth was supposed to be an ongoing role, as a foil for Kirk in many episodes of Star Trek: The Original Series. Early in the making of Star Trek, Gene Coon – producer on the first two seasons of TOS – devised the concept of the recurring Klingon nemesis, with actor William Campbell in mind. However, it was decided that, since Campbell's first season character of Trelane was so memorable, his return would be delayed until the second season. (Starlog #138, p. 34)
When David Gerrold wrote the script for "The Trouble with Tribbles", he did not spell out in the episode's dialogue the notion of Koloth as a regular foe. (Starlog #128) In fact, the installment's main Klingon character was initially intended to be played by Tige Andrews, though the episode couldn't be worked into his schedule. (The Star Trek Interview Book, p. 195)
William Campbell was then offered the part by Gene Coon. "It was almost a year to the month [after guest-starring as Trelane in "The Squire of Gothos"] that he called me about playing Koloth," said Campbell, who immediately accepted the role. (Star Trek Monthly issue 11, p. 52) Roughly eighteen months following his stint as Trelane, Campbell received another call from Coon about the possibility of featuring in half a season, beginning with "The Trouble with Tribbles". Campbell later clarified, "The reason for doing that show was not for doing 'The Trouble with Tribbles' – it was just a job. Gene said, 'Bill, it's not Trelayne, but we're starting to run out of stories. We may have to do what they did with Buck Rogers and take this Captain Koloth and make him the prime adversary.'" (Starlog #128)
Campbell subsequently attended a meeting about the character. "When I walked into the meeting," the actor stated, "they asked me what my conception of Captain Koloth was. 'Well, let me put it this way: I would never let anyone else hurt Kirk because I've got to hurt him – in fact, I'll never kill him because I want to make the suffering long.' They said, 'That's exactly what we want.'" (Starlog #128) Campbell further related, "I recall Gene [Coon] asking what I would do with the part. I said I wanted to play something like Flagg and Queeg from the old movie serials – always at each other's throats, but if someone beat up one of us, the other would rush to his aid, saying, 'No one's gonna beat him up but me!'" Coon was delighted with the concept they discussed. Happy to continue in the part, Campbell signed a deal with him for a total of thirteen episodes. (Starlog #138, p. 34) "I said I'd love it," Campbell noted. (Star Trek Monthly issue 11, p. 52)
Forging ahead with the plan of using Koloth as a recurring villain, Campbell worked out some details with William Shatner which influenced the on-screen depiction of the Klingon character's familiarity with Kirk (and vice versa). Said Campbell, "Gene [Coon] thought it was an element that had to be there whether it was referred to in the future or not." (Starlog #128)
As it turned out, Campbell found that depicting Koloth required "just coming in for a brief moment." (Star Trek Monthly issue 11, p. 52) The idea of continuing the character as a recurring presence was lost due to a changeover of producer in the third season, as the departure of Gene Coon led to the arrival of Fred Freiberger, who had his own ideas about how to carry on the series. (Starlog #138, p. 34) The plans to bring Koloth back on a recurring basis were obviously even more shattered by the cancellation of TOS. (Star Trek Monthly issue 11, p. 53) In hindsight, Campbell speculated, "What was great about the Koloth character was that I was the only one [of the Klingon-playing actors from TOS] who could possibly be a counterpart to Bill Shatner [....] My character age-wise and personality-wise would have been the Klingon equivalent to Captain Kirk." (Star Trek Monthly issue 11, p. 52) More specifically, Campbell envisioned that Koloth would have matched Kirk's charisma, strength and "sex appeal," he laughed. "I'm taking license here." (Starlog #138, p. 34) Campbell regarded the degree of similarity between Koloth and Kirk as a stroke of good luck and "the reason that Gene Coon asked" if he would be in thirteen episodes. (Star Trek Monthly issue 11, pp. 52-53) Concluded the actor, "Had they been continuing, I would have been signed for 13 episodes as Koloth and I would have liked to do that [....] I think Roddenberry zigged when he should have zagged. He never should have allowed the Kirk and Koloth thing to die there." (Starlog #128)
Koloth was not only portrayed by William Campbell; the character was also voiced by James Doohan in "More Tribbles, More Troubles", Koloth's single appearance in Star Trek: The Animated Series. The script for that installment introduces Koloth by describing him as a "polite Nazi bastard."
When it came time to cast DS9: "Blood Oath", William Campbell was harder to find than Kor actor John Colicos and Kang actor Michael Ansara. As a fan of Campbell's movie work from the 1950s, Ira Steven Behr was considerably annoyed that nobody even seemed to know who Campbell was. Eventually, official Star Trek historian Richard Arnold tracked Campbell down, thanks to the actor's participation in various Star Trek benefit events. (Cinefantastique, Vol. 25, No 6/Vol. 26, No. 1) Campbell was once again eager to accept the part. "I didn't hesitate for a second [....] I realized it would be to my advantage, not from a financial standpoint, although that comes into the equation, but to do something current for the fans. It gave me a whole new bunch of stories to tell [at conventions]." (Star Trek Monthly issue 11, p. 53)
Because the DS9 writing staff naturally had no foresight during the making of "Blood Oath" that they would later write "Trials and Tribble-ations", they chose to have Koloth killed by the end of the episode, which prevented the writers from later featuring him in a 24th-century plot thread in "Trials and Tribble-ations". This idea instead was ultimately written around the character of Arne Darvin. (The Magic of Tribbles: The Making of Trials and Tribble-ations)
Koloth was immediately popular, both with fans and with the creative team of TOS. (Starlog #138, p. 34) Joseph Pevney said of William Campbell's take on the character, "He was very good." (The Star Trek Interview Book, p. 195) Gowron actor Robert O'Reilly reckoned, "I guess Bill Campbell was my favorite Klingon." (The Official Star Trek: Deep Space Nine Magazine issue 16, p. 23) Campbell himself was taken by surprise at Koloth's longevity, conceding, "I never in my life thought that the Star Trek fans were going to remember Koloth." (Star Trek Monthly issue 11, p. 53)
According to the script for "Blood Oath", his name was pronounced as "KO-loth". 
The novel Forged in Fire detailed the friendship of Kor, Koloth, Kang, and Curzon Dax and the start of their blood feud with the Albino.
In the short story "The Unhappy Ones", Kor, Koloth and Kang were sent to Beta Thoridar to settle a dispute between the smooth-headed QuchHa' Klingons and the ridged HemQuch Klingons.