This thesis describes the development of psychological operations capabilities, introduction of forces, and the employment in Vietnam during the period 1960-1965. The complex interplay of these activities is addressed, as well as the development of PSYOP doctrine and training in the period prior to the introduction of ground combat forces in 1965. The American PSYOP advisory effort supported the South Vietnamese at all levels, providing access to training, material support, and critical advice. In these areas the American effort was largely successful. Yet, instability in the wake of President Ngo Dinh Diem's overthrow created an impediment to the ability of psychological operations to change behaviors and positively affect the outcome.