Every five year mission has its good and bad assignments, and Jim Kirk had his share of both

The Jupiter 2 Incident

Every five year mission has its good and bad assignments, and Jim Kirk had his share of both. If he had known that their rendezvous with the Tholian merchant ship would eventually lead to the advancement of a stagnating civilization, the freeing of thousands of slaves, a new dilithium-rich planet for the Federation, a closer Romulan/Federation relationship, a balance of power in the Organian Treaty Zone and the greatest discovery of the 23rd century: the finding of the long-lost Jupiter 2, Kirk would have put their latest assignment in the former category. But he didn't. There was nothing glamorous (or very ethical, in Kirk's mind) about transporting a shipload of Tholian rum to a backward planet which Starfleet had designs on signing into the Federation. In fact, Kirk could think of half a dozen better things to do with the Enterprise than assign her to a galactic packy run.