How did Senator Joseph McCarthy exercise his powers as committee chair?

Joseph McCarthy used his chairmanship of a Senate committee to conduct a Congressional inquiry into whether or not there were Communist sympathizers or agents in the US State Department and then the US Army. Congress has the power to investigate and gather information about any topic over which it has jurisdiction to pass legislation. To do this, Congress also has the power to subpoena witnesses before it. McCarthy used that subpoena power to He threatened various people that he would take them before his committee and make them testify under penalties of perjury as to their prior political associations. Many people were so afraid of being branded as a Communist sympathizer that they simply co-operated with his demands rather that stand up for their Constitutional rights. Even President Eisenhower at first was reluctant to stop McCarthy, because he did not want to be seen as a Communist sympathizer himself by stopping these investigations. .