The IKS Klothos was a Klingon battle cruiser commanded by Kor when he was in charge of the first of two Klingon divisions (the second being commanded by Kang) to participate in an attack against the Federation outpost at Caleb IV, successfully implementing the military stylings of an ancient Earth cavalry attack. The cloaking device was a new piece of technology to the Klingons at the time, and Kor was said to have spent three days in the engine room studying the device aboard the Klothos before the mission. (DS9: "Once More Unto the Breach")
Serving under Kor aboard the Klothos in 2269 were his first officer Kaz, and crewwoman Kali. The Klothos engaged the USS Enterprise in the Delta Triangle region, and both ships were pulled into the "triangle" during the battle. The crews of the Enterprise and Klothos were able to make a successful escape once they were able to set aside their differences and work together. (TAS: "The Time Trap")
Background
In "Once More Unto the Breach," an aged Kor said that the Klothos was a D5 class vessel, but the ship was seen in TAS: "The Time Trap" to be something closer to a D7 class. While there could have been two different vessels commanded by Kor, (just as James Kirk commanded two ships named Enterprise) a more elegant solution might be to say that Kor -- his senility being a key focus of the DS9 episode's plot -- confused the class name.
The incident at Caleb IV was not given a date in "Once More Unto the Breach," though it must have occurred at some point before peace was made between the Klingon Empire and United Federation of Planets in 2293. There is no way to know whether the events took place before or after the 2269 encounter in "The Time Trap."
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