“Effective 16 October 2006, Psychological Operations was established as a basic branch of the Army, pursuant to the authority of Section 3063(a)(13), Title 10, United States Code.”
That is the substance of General Order 30 (pdf) issued by Secretary of the Army Francis J. Harvey on January 12, 2007.
According to the Department of Defense Dictionary (JP 1-02), psychological operations are defined as “planned operations to convey selected information and indicators to foreign audiences to influence their emotions, motives, objective reasoning, and ultimately the behavior of foreign governments, organizations, groups, and individuals. The purpose of psychological operations is to induce or reinforce foreign attitudes and behavior favorable to the originator’s objectives. Also called PSYOP.”