Psychological warfare (PSYWAR), or the basic aspects of modern psychological operations (PsyOp), have been known by many other names or terms, including Military Information Support Operations (MISO), Psy Ops, political warfare, "Hearts and Minds", and propaganda. The term is used "to denote any action which is practiced mainly by psychological methods with the aim of evoking a planned psychological reaction in other people".
Various techniques are used, and are aimed at influencing a target audience's value system, belief system, emotions, motives, reasoning, or behavior. It is used to induce confessions or reinforce attitudes and behaviors favorable to the originator's objectives, and are sometimes combined with black operations or false flag tactics. It is also used to destroy the morale of enemies through tactics that aim to depress troops' psychological states.
Target audiences can be governments, organizations, groups, and individuals, and is not just limited to soldiers. Civilians of foreign territories can also be targeted by technology and media so as to cause an effect in the government of their country.
In Propaganda: The Formation of Men's Attitudes, Jacques Ellul discusses psychological warfare as a common peace policy practice between nations as a form of indirect aggression. This type of propaganda drains the public opinion of an opposing regime by stripping away its power on public opinion. This form of aggression is hard to defend against because no international court of justice is capable of protecting against psychological aggression since it cannot be legally adjudicated.
"Here the propagandists is [sic] dealing with a foreign adversary whose morale he seeks to destroy by psychological means so that the opponent begins to doubt the validity of his beliefs and actions."
There is evidence of psychological warfare throughout written history. In modern times, psychological warfare efforts have been used extensively. Mass communication allows for direct communication with an enemy populace, and therefore has been used in many efforts. In recent times, social media channels and the internet allow for campaigns of disinformation and misinformation performed by agents anywhere in the world.