"Alliances" is basically the secret origin of the Kazon. It's the episode where we discover how they became an intergalactic band of rival gangs, opportunistic thugs trying to survive by any means necessary, up to and excluding working together, even though this is an episode where Janeway tries to work with leaders from most of the sects, along with representatives of the Trabe.
Who're the Trabe? They're some persecuted aliens secretly manipulating Janeway in order to gain vengeance on the Kazon, even though they used to subjugate them and deserved the hard uprising that put them in that predicament in the first place. Suffice it to say, but if there had been a lot more Trabe in Kazon episodes, fans probably would've liked them better. But, as this is the only episode to feature them, it's an easy one to overlook.
The whole thing's really relevant because the season is about to plunge more heavily into its Kazon arc. "Maneuvers" was a good preview, but it doesn't really explain what's to come, other than that it'll involve Seska. "Alliances" is the beginning of the end of the Kazon in the series, and starts it off with a bang.
franchise * series * essential * character
Anthony De Longis
Memory Alpha summary.