The theft of the USS Defiant in 2371 by Thomas Riker, who posed as William Riker and used the ship for a Maquis raid into Cardassian space that uncovered a secret fleet.
The hijacking of the USS Defiant is the story of the Deep Space Nine episode Defiant. Thomas Riker, the transporter duplicate of William Riker who has joined the Maquis, visits the station in his counterpart's name, charms Kira Nerys into showing him the ship, stuns her and beams a Maquis crew aboard.
Benjamin Sisko travels to Cardassia Prime to help Gul Dukat hunt the vessel, since the alternative is war. Riker's real target is the Orias system, where he believes an illegal fleet is being built. An observer from the Obsidian Order forbids Dukat to send ships there, which shows that the fleet exists and belongs to the Order.
Sisko arranges a bargain. Riker gives up the Defiant and its sensor readings and accepts a life sentence in the labour camp on Lazon II, and his crew go free. The hidden fleet is seen again at the Battle of the Omarion Nebula.