Final answer:
J. Edgar Hoover was the head of the FBI for 50 years and played a significant role in combating crime and identifying potential threats to national security.
Step-by-step explanation:
The person being described is J. Edgar Hoover. Hoover joined the Federal Bureau of Investigation (FBI) when it was led by Attorney General A. Mitchell Palmer and they sought to expel radicals. Hoover later became the head of the FBI and held the position for 50 years. He is well-known for his long tenure as the director of the FBI, during which he focused on combating crime and identifying potential threats to national security.
Learn more about J. Edgar Hoover