President Harry Truman orders a "loyalty investigation" for all government employees and, further, if there are any "reasonable grounds" to doubt someone's loyalty that they be purged. Every department will have loyalty boards to conduct investigations.
According to the orders:
"The standard for the refusal of employment or the removal from employment in an executive department or agency on grounds relating to loyalty shall be that, on all the evidence, reasonable grounds exist for belief that the person involved is disloyal to the Government of the United States. ...
Membership in, affiliation with or sympathetic association with any foreign or domestic organization, association, movement, group or combination of persons, designated by the Attorney General as totalitarian, Fascist, Communist, or subversive, or as having adopted a policy of advocating or approving the commission of acts of force or violence to deny other persons their rights under the Constitution of the United States, or as seeking to alter the form of Government of the United States by unconstitutional means."