In the Pale Moonlight
Going over casualty lists, Sisko realizes there is only one hope of winning the war — the Romulans, who signed a non-aggression pact with the Dominion — must be convinced to join the Federation/Klingon Alliance. Sure that the Dominion will eventually invade Romulus anyway, Sisko recruits Garak to discreetly obtain evidence from Cardassia that will bring the Romulans into the war.
Sisko soon learns that several Cardassians expressed a willingness to help Garak, but all were killed within one day of speaking with him. Undaunted, Garak suggests that he and Sisko manufacture false evidence of an impending Dominion attack on Romulus, then call a secret meeting with a Romulan senator scheduled to be in the sector and present it to him. Frustration with the war convinces Sisko to agree, and when Garak recruits a condemned prisoner named Tolar to create the crucial evidence, the scheme begins.
Garak locates the Cardassian data rod necessary for the forgery, but Sisko must reluctantly trade a rare and dangerous compound for it. Then he, Garak, and Tolar get to work, creating a recording of a holographic meeting in which Weyoun, the Dominion leader, and Cardassia's Damar discuss plans to invade Romulus. Soon afterward, Senator Vreenak arrives.
Vreenak is condescending, sure that the Federation is about to fall to the Dominion. But when Sisko tells him the Dominion is planning to invade Romulus, Vreenak's mood changes. Sisko takes him to a secured holosuite and shows him the recording of the "meeting," after which Vreenak asks to examine the data rod. He later faces Sisko and announces that the rod is a fake.
A furious Vreenak leaves the station, vowing to expose Sisko to the entire Alpha Quadrant. Instead, the Romulan's shuttle explodes, killing him and damaging the forged data rod. An investigation points to the Dominion, but while the rest of his crew is ecstatic, Sisko is infuriated. He confronts Garak, who admits he suspected the rod might not pass inspection and placed a bomb on Vreenak's shuttle to guarantee the plan worked. Sure enough, it does — the Romulan Empire formally declares war against the Dominion. Sisko is upset to have lied and cheated, but with a possible victory finally in sight, he decides it's a feeling with which he can live.