Once again, we get a case study in what happens when an outside force interferes with the natural progression of a people. The people of the planet Ekos have begun patterning themselves after, of all things, Nazi Germany! And now one party is intent on committing genocide, utterly ridding themselves of the other! Kirk & Spock and the victimized Zeon people (and later, Bones) team up to prevent the worst from happening - as well as finding out where that outside force, an old mentor to Kirk, could have gone so wrong.
Interestingly, Roddenberry and episode writer John Meredyth Lucas take a rather controversial stance on how Nazi Germany could be seen as a model of efficiency. Kirk is aghast, while Spock considers the "practicality" behind such an approach: it might have worked with a much more benevolent leader at the helm.
'Patterns of Force' is another good example of how this series could maintain its appealingly campy, cheesy qualities while also ruminating on various serious issues in an intelligent, provocative way. It's an entertaining story that does offer some humor (the sight of Kirk, Spock & Bones in Nazi regalia, Bones' strained efforts to get his boots on, etc.) as well as the presence of the sexy Valora Noland ("The War Wagon"), some real tension, and a final message about the way that "absolute power corrupts absolutely"; in other words, that old mentor of Kirks' couldn't resist the chance to play God. It does suffer from a typical low episode budget. (You don't ever really believe that the principals are on another planet; it simply looks like they're revisiting Earths' past once again.)
Also guest starring Richard Evans ("Dirty Little Billy"), Skip Homeier ("The Ghost and Mr. Chicken"), and David Brian ("Flamingo Road").
Seven out of 10.