The Department of Justice unleashed a shocking and often violent unconstitutional nationwide dragnet — detaining as many as 10,000 people — on this day in history, Jan. 2, 1920.

Attorney General A. Mitchell Palmer, appointed to the office 10 months earlier by President Woodrow Wilson, led the sweep against suspected communists and anarchists, as well as their sympathizers.

The action was soon dubbed the Palmer Raids. 

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"The raids constituted a horrific, shameful episode in American history, one of the lowest moments for liberty since King George III quartered troops in private homes," writes the Foundation for Economic Education. 

The foundation calls the effort under President Wilson "America's reign of terror."

The Wilson administration also targeted political opponents.

"Even simple criticism of the government was enough to send you to jail," according to Christopher Finan, author of the 2007 book "From the Palmer Raids to the Patriot Act: A History of the Fight for Free Speech in America."

The Palmer Raids marked the height of the nation's first Red Scare, a response to the Bolshevik Revolution and communist takeover of Russia. 

The radical ideology soon spread across Europe and the United States after the tectonic social upheaval caused by World War I. 

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The era of fear was further fueled by widespread postwar labor discontent and the deadly influenza pandemic of 1919, which killed about 675,000 Americans, many of them children, in just a year-and-a-half.

"The Constitution faced a major test on this day in 1920 when raids ordered by Attorney General Mitchell Palmer saw thousands of people detained without warrants merely upon general suspicion," the National Constitution Center wrote last year. 

"Facilitated by a young Justice Department official, J. Edgar Hoover, what became known as the Palmer Raids peaked on the night of Jan. 2, 1920, when between 3,000 and 10,000 people in 35 cities were detained."

Many in the media applauded the raids. 

"There is no time to waste on hairsplitting over infringement of liberties," wrote The Washington Post on Jan. 4.

Alexander Mitchell Palmer was a Democratic congressman from Pennsylvania when Wilson chose him to head the Department of Justice. 

The Wilson administration called the new attorney general "young, militant, progressive and fearless."

The Department of Justice was accused of recklessly employing warrantless searches, illegal wiretapping and aggressive interrogation techniques that might be considered torture today. 

Palmer may have been motivated by personal revenge. 

"On June 2, 1919, a militant anarchist named Carlo Valdinoci blew up the front of newly appointed Attorney General A. Mitchell Palmer’s home in Washington, D.C. — and himself up in the process when the bomb exploded too early," the FBI reports in its online history of the bureau.

"A young Franklin and Eleanor Roosevelt, who lived across the street, were also shaken by the blast. The bombing was just one in a series of coordinated attacks that day on judges, politicians, law enforcement officials and others in eight cities nationwide."

Palmer was also motivated by personal ambition. 

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He launched his raids while beginning a bid for the White House.

He lost the Democrat nomination to James M. Cox at the party's convention in July. 

His "reign of terror" and White House ambitions ran out of steam simultaneously. 

"On April 30, 1920, Palmer warned of assassination attempts against ‘more than a score’ of government officials the next day. But on May Day, nothing happened, and Palmer lost momentum as a presidential candidate," according to the National Constitution Center.

He left office when Warren G. Harding became president in March 1921.

The Palmer Raids were deemed "lawless and subversive of constitutional liberty for citizens and aliens alike" during a Senate Judiciary hearing in February 1921.

The unconstitutional nature of the Palmer Raids were revived during the Franklin Delano Roosevelt administration in 1938 with the creation of the House Un-American Activities Committee under chairman and Texas Democrat Martin Dies. 

A new Red Scare consumed the government after World War II and the onset of the Cold War with the Soviet Union.

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The Truman administration and the HUAC would be accused of many of the same unconstitutional tactics as the Palmer Raids. 

"It originated with President Truman's Executive Order 9835 of March 21, 1947, which required that all federal civil service employees be screened for ‘loyalty,’" wrote Robert Justin Goldstein for Prologue magazine of the National Archives in 2006.

Attorney General Tom C. Clark issued his infamous "black list" the following December, officially known as the Attorney General's List of Subversive Organizations.

The highly publicized list, notes Goldstein, "cast a general pall over freedom of association and speech in the United States."

"The Palmer Raids were certainly not a bright spot for the young bureau," according to the FBI's online history of the department.

"But it did gain valuable experience in terrorism investigations and intelligence work and learn important lessons about the need to protect civil liberties and constitutional rights."