Initially, Joseph McCarthy focused on an investigation into communism's influence on "<span>government and security," since this was thought to be the most dangerous to national security. He then shifted focus somewhat to the entertainment industry. </span>
McCarthy made national headlines when he first accused over 200 members of the State Department of being communists. At the time of these accusations (aka the 1950's) the fear of communism was widespread in America. This was due to the United States rivalry with the Soviet Union for global influence. This rivalry was a result of World War II.
McCarthy used this fear to create investigative hearings, lead by Congress, that would call suspected communists to the stand in order to answer questions about their political affiliations or connections to the Soviet Union.