According to the U.S. Department of Defense, psychological warfare is the planned use of propaganda and other psychological actions having the purpose of influencing the opinions, behavior, and attitude of hostile foreign groups. Psyops can be used during conflict and peace times to control the behavior of not just groups and individuals but also whole governments.
Psyops have been used for thousands of years across many different nations and their wars. Alexander The Great conquered nearly the whole known world simply by spreading stories of his savagery. Later in history, Genghis Khan and the Mongols bloodily took over much of Asia and Europe. Though their reign was long and violent, they can attribute much of their success to their tactics in psychological warfare. By sending messengers ahead of the army to tell the villages ahead that the Mongol army was approaching. By the time the army arrived, towns were almost always ready to surrender.
For more about psyops take a look at this infographic. Let us know what you think in the comments and if you like what you see don't forget to like and share with your friends.