A covert mission in 2373 in which Benjamin Sisko and his officers, disguised as Klingons, entered the Klingon headquarters at Ty'Gokor and revealed that General Martok had been replaced by a Changeling.
The exposure of the Martok changeling is the plot of Apocalypse Rising, which opens the fifth season of Deep Space Nine. Odo believes he learned in the Great Link that Gowron is a Founder, and Starfleet sends Sisko to prove it. Sisko, Miles O'Brien and Odo are altered to look like Klingons, and with Worf they travel to Ty'Gokor.
They join the long celebration that precedes an Order of the Bat'leth ceremony, carrying devices whose radiation will force a Changeling to lose its shape. General Martok recognises them and has them arrested before they can use the devices.
In the cells Martok encourages Worf to kill Gowron in a duel instead. Odo notices that he seems unconcerned with honour and realises that the chancellor's name was planted in his mind. The false Martok is shot down by the assembled warriors, and Gowron agrees to talk about a ceasefire.