I didn't realize just how much of this episode was taken from The Enemy Below until I finally saw the movie (it has since become my fave war flick). There were a couple of elements lifted from Run Silent Run Deep as well. Nothing wrong with stealing ideas, as long as you do something cool with them. And boy did Roddenberry and company do something cool with this one.<br /><br />The story begins when the Romulans violate a 100-year old treaty and by crossing the neutral zone and destroying a series of Federation outposts along the zone, ostensibly to test their superior weaponry and invisibility screen (and subsequent shift in the balance of power between the Romulans and the Federation, in their view) as a prelude to an all-out invasion. Kirk has to decide whether it's worth risking war to try and stop the Romulan ship, or if in fact the greater risk lies in letting the invaders go after they destroyed 4 military outposts. Kirk wisely chooses the latter.<br /><br />This is our first look at an enemy of the Federation, the Romulans, a warlike, yet in their own way honorable race who are distant relatives to the Vulcans. However, unlike their peaceful cousins, the Romulans did not renounce their emotions and violent and imperialistic ways, even as they advanced technologically.<br /><br />None of this matters to Mr. Stiles, the ship's navigator and this episode's chief antagonist on board the enterprise (the Romulan commander has his own problems with a gung-ho junior officer). All that matters to him is he hates Romulans and Spock looks like one..until the end when Spock saves his life (naturally). This contrasts sharply with Captain Kirk and the Romulan commander, neither of whom has any personal ill will towards the other at all. Both men are simply doing their duty. In fact there's a mutual respect. This is the first Trek episode to deal directly with prejudice, and it does so deftly (as opposed to season 3's not-so-subtle "Let That be Your Last Battlefield").<br /><br />Like The Enemy Below, we have a classic chess match between two ship commanders who are actually very much alike. You see right away that both of these captains are good..VERY good. If you were going into battle you'd want either of these man as your leader. Both are honorable and decent men who are duty bound. Yet even though the Romulan commander is bound by duty to his home world, he still finds himself wishing for destruction before he can make it home rather than start another interstellar war. Yet he still does everything he can to make it home, just as Kirk does everything he can to stop him.<br /><br />This is, in my opinion, one of Trek's 5 best. It has everything: Plenty of action, suspense, great dialogue, fine acting (I still maintain the Romulan Commander was Mark Lenard's best Trek role), and it manages to make its social commentary without being overly preachy. A pity Roddenberry forgot about the last part when he did TNG.<br /><br />Watch this episode, then watch The Enemy Below.