Within days of Germany's World War II defeat, Winston Churchill ordered his aides to draft contingency plans for an Anglo-American invasion of the Soviet Union, a British newspaper reported Thursday.

Citing documents recently discovered in Britain's public archives, the Daily Telegraph said the plan, codenamed "Operation Unthinkable," was eventually rejected by Churchill and replaced with a defensive proposition to guard against invasion by Josef Stalin's Red Army.Historians had long believed that the tense period immediately after the war led to plans of this sort but had never been able to prove it until the forgotten documents were found, the Telegraph said.

"Nobody has ever seen this kind of thing before," the newspaper quoted war historian D.C. Watt as saying. "But we have had strong suspicions that they must have been written. I had always assumed that the records of this had been lost."

Churchill described the plan as "a purely hypothetical contingency," but regarded it as necessary enough to have his planning staff working on it amid the euphoria of victory, the Telegraph reported.

The battle plan, presented as a report to Churchill on May 22, 1945 - 14 days after the end of the war - included the use of up to 100,000 German troops to back up 500,000 British and American soldiers attacking through northern Germany, the newspaper reported.

It predicted that Stalin would invade Turkey, Greece, Norway and the oil fields of Iraq and Iran in retaliation and launch extensive sabotage operations in France, the Netherlands and Belgium.

The report assumed that the World War III would start on July 1, 1945, the Telegraph said, probably with a surprise attack by 47 British and American divisions.

The report ruled out total war against the Red Army, which outnumbered the Allies by more than 2-to-1, and added that an Anglo-American invasion of the Soviet Union probably would fare no better than Hitler's attempt in 1941.

John Ericson, an expert on the Soviet Union at Edinburgh University, described the documents as "very important and very illuminating," the Telegraph said.

"On June 29, 1945, the Red Army suddenly executed a complete redeployment of its order of battle, for no apparent reason," the newspaper quoted Ericson as saying. "I have always wondered why they did it. Perhaps we have just discovered the explanation."