Cardassian citizens watching propaganda broadcast over a viewscreen
Propaganda was a message that was used, especially in times of war, to influence the opinions of a populace.
Propaganda was used by both the Denobulans and the Antarans during the various wars between the two. (ENT: "The Breach")
A propaganda film was released in an alternate 1944 that promoted a prosperous alliance between Germany and America. (ENT: "Storm Front, Part II")
In 2151, Tolaris claimed that the Vulcan primal nature had been exaggerated by propaganda, in an attempt to dissuade the Vulcan people from looking deeper into it. (ENT: "Fusion")
In 2152, the spread of propaganda on an unnamed pre-warp planet was interpreted by the crew of the Enterprise that a war was coming between two nation-states. (ENT: "The Communicator")
Propaganda produced by the Klingon Empire in the 23rd century claimed that the United Federation of Planets committed atrocities against its prisoners, placing them in death camps and torturing them for their scientific and military secrets. (TOS: "Day of the Dove")
The Klingon-Cardassian Alliance used propaganda and Benjamin Sisko once referred to the Alliance as having a "propaganda machine". (DS9: "Through the Looking Glass")
The Cardassian Union has used propaganda to influence its citizens for a long time. Propaganda was often broadcast over large viewscreens. Dukat's first speech as the leader of the Cardassian Union was shown in such a way. (DS9: "Tribunal", "Second Skin", "By Inferno's Light")
In 2373, Kira Nerys hoped that Tekeny Ghemor would be able to "issue corrections" to the propaganda of the Cardassian Union. Unfortunately, Ghemor died of Yarim Fel Syndrome soon after he visited Kira on Deep Space 9. (DS9: "Ties of Blood and Water")
In early 2374, Jake Sisko was concerned that instituting Weyoun's proposed changes to his Federation News Service articles would make them "Dominion propaganda". Weyoun claimed that he "would never dream of asking" him to write such a thing. (DS9: "A Time to Stand")