Star Trek: Deep Space Nine: Season 4, Episode 2 - ProjectFreeTV

4 - 2: The Way of the Warrior, Part II

Believing that the recent Cardasssian coup was orchestrated by the Dominion, the Klingon decision to attack Cardassia puts the Federation-Klingon alliance in jeopardy, and forces Worf to choose between his people and his oath to the Federation.