The title comes from The Life and Adventures of Nicholas Nickleby by Charles Dickens: “It is an errand of mercy which brings me here. Pray, let me discharge it.” This ep is commonly known as “The Vietnam Story,” for its obvious allusions to Vietnam and its abuse by colonial powers. The Klingons and the Federation are poised on the brink, and then war is declared. Kirk and Spock visit Organia, a planet which lies on a tactical corridor likely to be important in the coming conflict. The Organian village was to be modeled on old English villages, w/ thatched huts and muddy back alleys. The simple/pastoral Organians are unconcerned by the threat of the Klingon occupation. Kirk has to hold in his anger when Kor interrogates him, as he is pretending to be passive like the Organians. Later in the street, Spock gets between Kirk and a Klingon warrior, so they don’t fight. Finally, Kirk and the Klingon commander Kor (Johm Colicos) learn why, and the reason will change Federation/Klingon relations!
Kor: Where is your smile?
Kirk [posing as an Organian]: My what?
Kor: The stupid, idiotic smile everyone else seems to be wearing.
This ep introduces the Klingon Empire; Klingons were named after creator/producer Gene Roddenberry’s friend, Bob Clingan. D.C. Fontana thought the Klingons were made the regular adversaries of the series b/c they didn’t need any special (and expensive) make-up like the Romulans, whom she thought to be more interesting. Colicos intended to reprise the role of Capt. Kor in a later, Day of the Dove, but he had a scheduling conflict. The role of Capt. Kang was written to take the place of Kor. The actor who played Kang, Michael Ansara, was of Arab descent and married to actress Barbara Eden (best known as Jeannie). Colicos reprised the role of an elderly Kor in a few eps of Star Trek: Deep Space Nine. The baldric that Kor wore was reused for Worf during S1 of Star Trek: The Next Generation. When it was exhibited at the Smithsonian Institution in the ’90s, the material could clearly be seen to be burlap sacking, painted gold.
[1] This episode resides at the top of the heap of Trek. Here is a well-paced, tension-filled, logical plot with good characters and an intriguing riddle at its core. John Colicos gives a simply great performance… And he gets the all time great line in Trek: “I don’t trust a man who smiles too much.”
[2] Kirk describes their society as a military dictatorship and there are parallels to Nazi rule in Europe during World War II.
[3] The Organian’s prove to be more interesting than they first appear, although I’m sure most viewers will have guessed that they aren’t quite what they seem long before the reveal.
-Excerpts from IMDB reviews
Knightleyemma 
Well into the late 70s most prime-time TV was written so you didn’t have to know much about the history of the characters to appreciate it. (Daytime soaps were an exception). Then towards the middle / end of the 70s evening soaps became really popular, and that had a big influence on how episodes were written — suddenly they had continuity!
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The way I saw these (in syndication) they were never shown in order, so the “introduces the Klingons” thing was lost on me at the time. (To me it’s so interesting that people mostly watch TV episodes in order now — they weren’t necessarily written with that expectation.) However, this episode is consistently rated among the best of the show and I agree.
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I’m watching (2nd time) on Netflix; they put “The Cage” as E1 (which doesn’t make sense at all, unless you know some of the ST:TOS show history). This show doesn’t need to be seen in order, like most of the “Law & Order” series (though unlike ST:DS9 w/ its several story arcs).
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