DS9 Season 6 Episode 19 In the Pale Moonlight

Plot

The episode is told in flashback, as Sisko records a personal log entry on the events of the past two weeks.
The losses suffered by the Federation in the Dominion War are taking their toll. To turn the tide of the war, Sisko decides that he must bring the Romulans into the war on the Federation's side no matter what.
To do so, he will need evidence that the Dominion plans to attack the Romulans. Sisko enlists Garak's help to find this evidence, but all of Garak's contacts end up dead shortly after communicating with him. Garak suggests they forge a recording of Dominion leaders discussing a surprise attack. Hesitant, but driven forward by the Dominion's recent conquest of Betazed, Sisko obtains permission from Starfleet to proceed.
At Garak's request, Sisko secures the release of a forger named Grathon Tolar from a Klingon prison. In order to obtain an authentic Cardassian data rod, he is forced to trade a large quantity of bio-mimetic gel, a rare, dangerous, and highly regulated material, over Dr. Bashir's protests. When Tolar stabs Quark in an altercation while drunk, Sisko bribes Quark to drop the matter.
Tolar forges a holographic record of a meeting between Dominion leaders discussing plans to invade Romulus. Meanwhile, on Garak's advice, Sisko arranges a secret meeting with Vreenak, an influential Romulan senator. Sisko gives Vreenak the recording, but the senator discovers the forgery and vows to expose the deception. As Sisko faces the possibility that his actions may actually force the Romulans to side with the Dominion, he learns that Vreenak's ship was destroyed en route home.
Sisko confronts and punches Garak, who admits he planted a bomb on Vreenak's ship. Garak explains that when the Romulans scan the wreckage and find the rod, any imperfections will be attributed to damage from the explosion, and the Romulans will assume that the Dominion assassinated Vreenak to prevent him from bringing the rod back. Thus, the recording will implicate the Dominion as planned. Garak tells Sisko he can ease his conscience with the knowledge that the Alpha Quadrant may have been saved, at the cost of the lives of Vreenak and Tolar (whom Garak has also killed) and Sisko's self-respect—which Garak calls a bargain.
Soon, the Romulans indeed do declare war on the Dominion. At the end of his log entry, Sisko wrestles with having condoned forgery, bribery, and murder for the good of the Alpha Quadrant, and, after thinking about it, declares that he can live with it. He then deletes the entire personal log.