Star Trek: 25 Greatest Next Generation Episodes
19. The Wounded
In the first outing with the Cardassians, the Federation conflict with them having just recently ended, a Galor class ship opens fire on the Enterprise having apparently not gotten that message, but it turns out it was a Federation starship that provoked the attack.
The captain of the U.S.S. Phoenix, Benjamin Maxwell (played by Bob Gunton, the Shawshank warden and secretary of defense in 24) lost his entire family in the recent war and convinces himself that the Cardassians are arming for war again. It is only Chief O'Brien, Maxwell's tactical officer on his last command, who can manage to talk some sense into him without beginning a one man campaign of war and genocide.