Historians and biographers of General George S. Patton are panning Bill O'Reilly's theory that the World War II commander was assassinated by the Soviet Union, calling the tale implausible and lacking evidence.

Most historians stick to the long-held evidence that Patton died from complications after a December 1945 car accident that left him paralyzed.

But O'Reilly and co-author Martin Dugard contend in the newly-released Killing Patton that the general's death was the result of a conspiracy by former Soviet leader Joseph Stalin. O'Reilly repeated the theory during an appearance to promote his book on ABC News' This Week:

STEPHANOPOULOS: The official record says Patton died after a car accident on a hunting trip, but O'Reilly's new book “Killing Patton” suggests a darker conspiracy. O'REILLY: I think Stalin killed him. Patton was going to go back to the United States and condemn Stalin and the Soviet Union, tell the American people these guys aren't going out of Poland, they're going to try to take over the world. And Stalin wanted him dead. And I think Stalin got him dead.

Several historians who have researched Patton's life told Media Matters no real evidence exists to support O'Reilly's claim.

“Premising an assassination plot on something so uncertain as a traffic accident doesn't seem plausible,” said Jonathan W. Jordan, author of Brothers Rivals Victors: Eisenhower, Patton, Bradley and the Partnership that Drove the Allied Conquest in Europe. “The rapid onset of Patton's death is not inconsistent with a pulmonary embolism ... There is no smoking gun pointing toward poison smuggled into his Heidelberg hospital room. Exhumation and testing of Patton's body, while it would put the matter to rest, most likely would be a biological Al Capone's Vault.”

Rick Atkinson, a historian and author of several books about World War II, agreed saying Patton's death was from injuries suffered in “a fender bender, outside Heidelberg, in the fall of 1945.”

Robert H. Patton, the general's grandson and author of The Pattons: A Personal History of an American Family, said both research and family lore discredit O'Reilly's version of events.

“Generally growing up our sense was the general's widow was satisfied that it was accidental,” he said. “She was persuaded that it was an accident.”

Robert Patton said his grandfather suffered from Phlebitis due to a blood clot he developed from a fractured leg between World War I and World War II. He said after he was paralyzed in the auto accident it worsened and eventually led to his death.

“The theory is he either died naturally or from a blood clot,” the younger Patton said. “You're paralyzed, and that is what happens. My grandmother was with him constantly in the hospital.”

Carlo D'Este, author of Patton: A Genius for War, said there was no reason for an assassination since Patton was close to death.

“You've got to look at what Patton's situation was. He was a quadriplegic, he was going to die anyway, he was totally immobilized, he couldn't move,” said D'Este. “What is the point of assassinating him and where did Stalin come from anyway? There have been a lot of claims made over the years and here is a new one. Sure, somebody could have snuck in the hospital, but why would you bother? You need to verify facts. That certainly raises a red flag with me.”

O'Reilly's book has also drawn criticism for lauding Patton while failing to note the general's anti-Semitism, a critique recently leveled by Washington Post columnist Richard Cohen.