"Propaganda is the expression of opinions or actions carried out deliberately by individuals or groups with a view to influence the opinions or actions of other individuals or groups for predetermined ends through psychological manipulations."

Lasswell made these contributions to the field of communication study:

His five-questions model of communication led to the emphasis in communication study on determining effects. Lasswell’s contemporary, Paul F. Lazarsfeld, did even more to crystallize this focus on communication effects.
He pioneered in content analysis methods, virtually inventing the methodology of qualitative and quantitative measurement of communication messages (propaganda messages and newspaper editorials, for example).
His study of political and wartime propaganda represented an important early type of communication study. The word propaganda later gained a negative connotation and is not used much today, although there is even more political propaganda. Propaganda analysis has been absorbed into the general body of communication research.
He introduced Freudian psychoanalytic theory to the social sciences in America. Lasswell integrated Freudian theory with political analysis, as in his psychoanalytic study of political leaders. He applied Freud's id-ego-superego via content analysis to political science problems. In essence, he utilized intraindividual Freudian theory at the societal level.
He helped create the policy sciences, an interdisciplinary movement to integrate social science knowledge with public action. The social sciences, however, generally resisted this attempt at integration and application to public policy problem.
src: wiki 20180329