As a boy I rated this as one of my favorite TREK episodes, just because there's plenty of action, lots of gun play and because Kirk genuinely does make (in Spock's words) "a very convincing Nazi." Interestingly, when I began to recreate my Star Trek collection on video, twenty years later, I found that PATTERNS did not live up to my memories. I think part of the problem is that the treatment of Nazism is meant to be challenging and serious but actually pulls some punches.
Several reviewers correctly pointed out that the real Nazi Germany was in fact NOT "the most efficient state earth ever knew." But the differences between the "real" Nazi Germany and Professor Gill's Ecosian variety are also interesting. The horror of the real Holocaust is toned down in several ways.
1.) The Zeons have a planet of their own, and presumably could always find some way to hide and/or fight back in an emergency, (such as an extraterrestrial invasion) however "peaceful" they might be.
2.) The Zeons we meet on this planet, Isok, Abram, and the rest, are all openly militant, determined to fight back, well organized, and completely un-intimidated by Brown Shirts and SS. There's not even a hint of passivity, terror, or a state of denial comparable to what crippled Europe's Jewish population with such tragic results. (i.e. "this too will pass, they can't be serious, they really need us.")
3.) The anti-Nazi resistance in Germany was pathetically ineffectual (with apologies to the brave Von Stauffenberg.) But the story line here softens the historical truth. It seems the Ecosian Nazi party is riddled with resistance members, double agents, and free spirits of all types. One minute it's lovely Dara who's switching sides, and the next thing you know Party Chairman Enig is "one of us" too. Kirk and Spock could have stayed on the Enterprise and "phoned it in" if they had known defeating the Nazi menace would be this easy!
4.) Given that there are plenty of heroic Zeons and noble Ecosians to do the heavy lifting, it's a real shame Kirk couldn't have had a love scene or two with Dara, the ultimate Kitten With A Whip. Come to think of it, if SHE had been in charge of the "whipping" scene this episode would have definitely broken new ground!