In “Young J. Edgar: Hoover, the Red Scare, and the Assault on Civil Liberties” (Carroll & Graf, 496 pages, $28.95) Kenneth Ackerman plays to his strengths. He has served more than 25 years in senior posts on Capitol Hill and in the executive branch, as well as in private practice as a Washington, D.C., attorney, and the result is a chilling account of how the rule of law in a war on terror can be subverted into a war of terror.

Mr. Ackerman traces Hoover’s rise from 1917 as a young attorney in the Department of Justice, to his appointment in 1921 as deputy director of the Bureau of Investigation, to his promotion in 1924 as director of the Federal Bureau of Investigation. A hard worker superb at navigating the federal bureaucracy, Hoover made himself indispensable not long after Attorney General A. Mitchell Palmer decided to implement his infamous raids (“the Red Scare”) in November 1919.

At first, Mr. Ackerman acknowledges, the raids were “applauded by top officials in government, media, business, academia, and religion, almost across the board.” In the aftermath of the Russian Revolution, anarchists and communists in this country spoke openly about violently overthrowing the American government. A series of riots and bombings seemed to signal that the Reds were advancing toward their goal.

Palmer, a Woodrow Wilson progressive, had resisted calls for a government crackdown on radicals. But when his own home was bombed and he realized that he and his family had narrowly escaped death, he decided that nothing less than an extermination of the Red threat could secure his government’s survival.

Implementation of extralegal procedures seemed essential. Or as Mr. Ackerman puts it:

There is a seductive downward spiral in times of crisis from ‘doing something’ to ‘doing what it takes’ to ‘doing anything.’

Abetted by Hoover’s dogged surveillance of radicals and by his extraordinary record-keeping and filing apparatus, Palmer had plenty of people to round up. Mr. Ackerman provides a persuasive account of Palmer’s mindset and why it led to a “civil liberties catastrophe”:

Probable cause to get a search warrant or an arrest warrant, providing prisoners a fair trial, including access to a lawyer … these rules can seem arcane and counterproductive when they occasionally get in the way, stopping police from preventing a crime, helping a guilty person go free, or interfering in the tracking of a possible terrorist. But they serve an essential purpose: they force the government to get its facts straight before it deprives any person — citizen or immigrant — of his or her freedoms, locks them up, deports them, seizes their property, or invades their privacy.

On January 2, 1920, Hoover sent federal marshals to arrest 2,700 suspected communists in 33 cities A later raid rounded up another 3,000. Many of the arrested were union leaders and immigrants and their crime was, at worst “guilt by association,” as Mr. Ackerman notes.

Not only did Hoover continue to feed Palmer’s enthusiasm for the raids, he lied about his part in this despicable episode. Later he would use many of the same illegal methods to pursue suspects throughout his five decades as FBI director. Mr. Ackerman calls the attorney general’s reliance on the 24-year-old Hoover Palmer’s biggest single mistake. “Despite his clear genius for organization,” he writes, “Edgar lacked the other essential qualification for the job, the life experience and human context to appreciate the responsibility that came with power.”

As hard as Mr. Ackerman is on Hoover, he does not demonize him. The biographer’s own “life experience” and knowledge of power tell him that men like Hoover result from how their superiors deport themselves. Thus Mr. Ackerman excoriates Woodrow Wilson’s “loyalists” for creating the myth that the president “had nothing to do with” supporting the Palmer raids. If so, Mr. Ackerman insists, “it was only because he [Wilson] kept himself ignorant, not because Mitchell Palmer refused to tell him.”

Mr. Ackerman finds Hoover’s immediate superiors even more culpable: “There were at least five people in the Justice Department who outranked Edgar at the time. … But none of them objected. Instead, they let Edgar call the tune from below” — a point that attorney Jackson Ralston made clear testifying before Congress in 1921, when the public and Congress turned against Palmer’s violation of the Constitution.

That Mr. Ackerman has a moral with an urgent contemporary ring is apparent in his conclusion: “To the extent that our modern war on terror is paralleling the attitudes of the 1919-1920 Red Scare, we have to wonder: How many young J. Edgar Hoovers are we creating today?”

crollyson@nysun.com