Synopsis:

The Enterprise approaches Ekos to check on Federation Observer John Gill.   John Gill has been sent to watch the development of the primitive and warlike Ekosians.   The Ekosians have been being helped in their development by the Zeons, a species from another planet in the system.  Now, however, the Ekosians have become a Nazi dominated planet which plans to conquer the Zeons.

Personally I really liked this episode because I am a fan of history in general and W.W.II in particular. Also there are some fairly interesting and humorous situations that arise during an otherwise tense show.   This is one of those shows to gather together in the "Star Trek uses history to make a cheap episode" night.   But, like many of the others it is still a well done and enjoyable show.