In the United States, Red Squads were police intelligence units that specialized in infiltrating, conducting counter-measures and gathering intelligence on political and social groups during the 20th century. Dating as far back as the Haymarket Riot in 1886, Red Squads became common in larger cities such as Chicago, New York, and Los Angeles during the First Red Scare of the 1920s. They were set up as specialized units of city police departments, as a weapon against labor unions, communists, anarchists, and other dissidents.
In New York, former City Police Commissioner Patrick Murphy traced their origin there to an "Italian Squad" formed in 1904 to monitor a group of Italian immigrants under suspicion. However, it is their association with fighting communism which provides the basis for the name "Red Squad." They became more commonplace in the 1930s, often conceived of as a countermeasure to Communist organizers who were charged with executing a policy of dual unionism - namely, building a revolutionary movement in parallel with membership in above-ground labor organizations. Similar units were established in Canada in this period, although only the Toronto police under Chief Dennis Draper used the name.
In the late 1960s, as the protests against Vietnam and the general domestic upheaval intensified, the Red Squads augmented their focus, to include dissidents largely outside the labor movement, including therein not just war resisters, but protest movements of all political stripes, including Neonazis, Native American movements, the women's movement, environmentalists, the civil rights movement, and others. The methods employed ranged from simple surveillance to isolated incidents of assassination. Anti-activist police operations were expanded under the Johnson and Nixon administrations, particularly in concert with, and within the cadre of the FBI's COINTELPRO surveillance program, but also including domestic spying by the CIA.
After the civil unrest during Johnson's administration, Watergate during Nixon's administration, and the public exposure of COINTELPRO by a dissident organization in 1971, widespread criticism of the Red Squads for illegal and undemocratic tactics emerged. In 1975, in the wake of both the Watergate scandal and the exposure of COINTELPRO, the Church Committee was formed to investigate overstepping on the part of federal law inforcement and intelligence gathering agencies. Following the recommendations of that committee, the U.S. Congress passed Foreign Intelligence Surveillance Act (FISA) in 1978, placing limits on the power of police and Federal agencies. This ended the official use of Red Squads.
Since 1978, the term Red Squad has resurfaced repeatedly to describe any action by police or Federal agencies that is deemed to be oppressive to a social or political group.
The term Red Squad has been used to describe New York City Police Department infiltration of liberal groups, first in preparation for the 2004 Republican National Convention and then continuing until today.
It has been alleged that Red Squad style social control activity has reemerged as what is described as “gang stalking.” A former high ranking FBI agent, Ted Gunderson, submitted an affidavit on the issue to a Freedom of Information Act request. The case, No. 10-00169, is pending. Additionally, a private investigator, David Lawson, wrote a book about his investigation into these groups. There are also several victim’s websites and news stories  making similar accusations. All sources believe these groups are citizen based, but some claim they are sanctioned by elements within the U.S. Government.
- Church Committee
- Domestic Security Enhancement Act of 2003
- Haymarket Riot
- Patriot Act
- Red Scare
- Surveillance abuse
- Will v. Michigan Dept. of State Police, 491 U.S. 58 (1989)
- "Police Surveillance of Political Activity -- The History and Current State of the Handschu Decree". Testimony Of Arthur N. Eisenberg Presented To The New York Advisory Committee To The U.S. Commission On Civil Rights. New York Civil Liberties Union. May 21, 2003. Archived from the original on August 28, 2006. Retrieved February 19, 2007.
- "Blog Archive » They Pat Some Good Boys On the Back and Put Some to the Rod". Balloon Juice. 2012-03-24. Retrieved 2012-07-25.
- Report: NYPD infiltrated liberal groups
- "Freedom of Information Request No. 10-00169 to DOJ Office of Justice Programs via a letter received at OJP March 22, 2010 (by Attorney Keith Labella, Esq.)" (PDF). Retrieved 2012-07-25.
- "Cause Stalking (9780970309259): David Lawson: Books". Amazon.com. Retrieved 2012-07-25.
- "Gang Stalking and Electronic Technological Harassment on national TV". YouTube. 2010-08-19. Retrieved 2012-07-25.
- "Gang Stalking, Bullying on Steroids". LiveLeak.com. Retrieved 2012-07-25.
- Frank J. Donner (1990). Protectors of privilege : red squads and police repression in urban America. University of California Press. ISBN 0-520-05951-4. Includes bibliographical references.
- Encyclopedia of Chicago: Red Squad
- Red Squad. Directed by Steven Fischler, Joel Sucher, Howard Blatt and Francis Freedland. USA, 1972, b/w, 45 min.
- "Police Surveillance of Political Activity -- The History and Current State of the Handschu Decree, Testimony Presented To The New York Advisory Committee To The U.S. Commission On Civil Rights", Arthur N. Eisenberg, New York Civil Liberties Union (May 21, 2003)
- Fighting Terror With Databases; Domestic Intelligence Plans Stir Concern, Jim McGee, The Washington Post (February 16, 2002)
- "Hate Squad", Reason Magazine, Charles Paul Freund (2001)
- "Now Police Can Spy On Everybody", Leonard Levitt, New York Newsday (February 12, 2003)
- "NYPD fights ban against spying on activists", Oliver Burkeman, The Guardian (November 30, 2002)
- "Return of the Red Squad", Socialist Worker, Nicole Colson, (February 27, 2004)
- "Rules Eased for Surveillance of New York Groups", Benjamim Weiser, New York Times (February 12, 2003)
- "The NYPD Wants to Watch You", Nation's Largest Law Enforcement Agency Vies for Total Spying Power, Chisun Lee, Village Voice, December 18–24, 2002.
- "Red Squad Returns", The Indypendent, July 4, 2003