PALMER RAIDS—1919-20

As part of the Red Scare, thousands of suspected radicals are rounded up by FBI agents and auxiliaries. The adverse public reaction teaches J. Edgar Hoover a lesson in professionalism and highlights for the nation the issue of maintaining civil liberties during a crisis.

JOHN DILLINGER—1934

The hunt for the famous bank robber pushes the federal government into criminal law enforcement. The FBI gains full-fledged police powers during the investigation, and the resulting G-man myth shapes public perception of the Bureau for years.

ALGER HISS—1949

Three hundred FBI agents gather evidence against the State Department official accused of perjury over his Communist-party involvement. The Bureau’s assistance helps give credence to the Red Scare that culminates in the McCarthy hearings five years later.

COINTELPRO—1956

In setting up a counterintelligence program directed at the Communist party, the Bureau moves decisively away from legitimate law enforcement and toward becoming a political police force. COINTELPRO’S abuse of power and official lawlessness continues for 15 years, targeting a variety of groups.

MISSISSIPPI BURNING—1964

Code name for the investigation into the kidnapping and murder of three civil rights workers near Philadelphia, Mississippi. More than 250 Bureau agents work on the case, implicating local police and Ku Klux Klansmen. This marks the beginning of a stepped-up effort by the Bureau to combat violence against the civil rights movement.

ABSCAM—1978-80

Following Watergate-era reforms, the FBI increases its attention to white-collar crime and corruption among public officials. The operation introduces new techniques—the use of undercover agents and sting operations—and leads to guidelines for their use.

LA COSA NOSTRA—1986

Focusing on top mob bosses and their operations, the FBI uses meticulous surveillance and tapes of conversations to build a complex case that ends in the conviction of eight leaders of Mafia “families.”

THE WORLD TRADE CENTER BOMBING—1993

After a concerted effort by hundreds of agents, the FBI arrests a suspect six days after the New York City bombing. Further investigation penetrates the conspiracy, preventing further terrorist incidents and leading to more arrests and convictions.

WACO—1993

The 51-day standoff with religious fanatics in Texas, supervised by the FBI’s Hostage Rescue team, ends in disaster, with 80 persons killed. Waco becomes emblematic of FBI blunders in the 1990s, which tarnish the Bureau’s image and point out the need for reforms.

SEPTEMBER 11—2001

The most comprehensive investigation in the Bureau’s history, the case is speeding a shift, once again, toward intelligence gathering as opposed to law-enforcement duties. It emphasizes the need for interagency cooperation and highlights the growing international reach of the FBI’s responsibilities.

— J.K.