NEW YORK — World War II documents released this week indicate Britain and the United States knew ahead of time that Germany planned to exterminate Rome's Jews.

They also reveal candid conversations among German prisoners of war, including graphic descriptions of how Jews were executed during the war.

According to records, British intelligence knew in late 1943 of German plans to deport Roman Jews to the Auschwitz death camp in Poland, and shared this information with United States. Neither country took steps to warn the Germans or inform the Italians.

"I understand that the British were trying to protect the secrecy of their code-breaking operations," said Richard Breitman, a professor of history at American University in Washington. But Breitman said the British had other methods of leaking the information, and had used those in the past.

The Nazi War Criminal Records Interagency Working Group released 400,000 pages of documents, the largest of its kind, to comply with the Nazi War Crimes Disclosure Act of 1998. The documents were culled from records of the Office of Strategic Services, a forerunner to the CIA.

Among these are secret tape recordings by the British of frank conversations between captured German prisoners who often gave "minimized" accounts of their actions during the Holocaust to Allied investigators to avoid prosecution, said Eli Rosenbaum, director of the U.S. Justice Department's Office of Special Investigations.

"How was it done?" asked one prisoner, concerning executions in a town in Latvia.

"[The Jews] faced the trench and then 20 Latvians came up behind and simply fired once through the back of their heads," answered the second prisoner.

"There was a sort of step in the trench, so that they stood rather lower than the Latvians, who stood up on the edge and simply shot them through the head, and they fell down forward into the trench. After that came 20 men," and then "someone gave the command and the 20 fell into the trench like ninepins."

Later, the second prisoner said of the executions, "We draw our drinking water from deep springs; we're getting nothing but corpse water there."

According to Breitman, although there is overwhelming evidence that many German soldiers were involved in the Holocaust, the documents also indicate there was opposition to Nazi atrocities.

Tullia Zevi, former president of the Union of Italian Jewish Communities, said the recent revelation was no surprise, coming as a "confirmation of what was practically known," but it could clarify many "blurred" aspects of the war and the Shoah.

"What we know less is the reaction of the recipients. How was this news received? Was there even a blink of moral indignation? Did they intend to protest?" Zevi noted.

The documents are now available to researchers at the National Archives in College Park, Md.