A week after US troops were sent to fight in far-away country, the FBI proposed to the president that 12,000 people be rounded up and detained as "potentially dangerous" to national security. Almost all of them were citizens, and the FBI proposed that the president suspend habeas corpus to make the roundup constitutional.

The president, however, was not George W. Bush, and the war in question was not the war on terror – it was the Korean War.

The plan, outlined in a 1950 letter from FBI Director J. Edgar Hoover to an assistant to President Harry Truman, called for "permanent detention" of the 12,000. That was deemed necessary to "protect the country against treason, espionage and sabotage."

Hoover told Truman that the FBI had spent "a long period of time" creating a list of "approximately twelve thousand individuals, of which approximately ninety-seven per cent are citizens of the United States." The 12,000 names were not included in the proposal that was declassified on Dec. 22.

The equivalent proportion of the population today would be 25,000 people.

What would such a roundup look like? Now we know: Hoover was concerned about making sure it would hold up in court. The way to do that, he wrote, was the president would issue a proclamation that "recites the existence of the emergency situation and that in order to immediately protect the country against treason, espionage and sabotage, the Attorney General is instructed to apprehend all individuals potentially dangerous to the internal security." In order for that to be legal, the president’s proclamation would suspend habeas corpus.

Then Congress would pass a "joint resolution" supporting the roundup, and the president would issue an executive order to the FBI to go to work.

Hoover’s other concern was where to jail 12,000 people. So many of the people on the lists lived in New York City, Los Angeles and San Francisco that prisons there weren’t big enough to hold all of them. So for the targets those cities, Hoover proposed "detention in military facilities."

Although George W. Bush was only four years old at the time, the 1950 plan has some striking parallels to his policies today. After 9-11, as Tim Weiner of the New York Times explained, Bush "issued an order that effectively allowed the United States to hold suspects indefinitely without a hearing, a lawyer, or formal charges." Last year Congress passed a law formally suspending habeas corpus for anyone named by the president as an "unlawful enemy combatant." The Supreme Court is reviewing that law this term.

There are significant differences, however: Hoover’s 1950 plan required "a statement of charges to be served on each detainee and a hearing to be afforded the individual within a specified period."

And there’s one other difference between the 1950 plan and our present war on terror: President Truman ignored the FBI proposal and never went to the Supreme Court to argue that habeas corpus did not apply to people detained as threats to the country.

Hoover’s letter was included in the latest volume in the State Department series "Foreign Relations of the United States" released on Dec. 22 with the modest title "The Intelligence Community, 1950-1955." The volume is 759 pages long and is online; the Hoover letter can be found here on page 18. New York Times reporter Tim Weiner gets credit for discovering the Hoover letter — he reported the story on Dec. 23.