Final answer:
J. Edgar Hoover made significant changes to the FBI's employment policies, introducing thorough vetting and competitive exams for hiring and promotions to professionalize the agency and reduce corruption.
Step-by-step explanation:
When J. Edgar Hoover became the Director of the Federal Bureau of Investigation (FBI), he enacted significant changes in the agency's employment policies. During his tenure, especially in the early months, Hoover demonstrated a reformist spirit, continuing civil service reform by introducing a more rigorous vetting process for hiring new agents and implementing competitive exams for promotions. These changes were part of a broader effort to professionalize the FBI and reduce corruption within the federal government. Moreover, Hoover's FBI focused on internal security during the Cold War era by investigating and conducting surveillance on alleged communists and other perceived threats within the United States, expanding the scope of the Bureau's involvement in the lives of American citizens.