Walter Isaacson's highly anticipated biography on Elon Musk is hitting shelves on Tuesday — and he is already walking back a major claim.

Isaacson reported in his book that Musk had abruptly turned off Ukraine's access to his Starlink satellite internet system last year just as the country was launching an underwater drone attack on a Russian fleet in Crimea, depriving the Eastern European country's forces of critical communications for the assault and rendering the offensive a failure.

"He secretly told his engineers to turn off coverage within 100 kilometers of the Crimean coast," fearing the sneak attack would lead to a "mini-Pearl Harbor" scenario and nuclear war, Isaacson wrote in the book, according to an excerpt obtained and first reported by CNN. "As a result, when the Ukrainian drone subs got near the Russian fleet in Sevastopol, they lost connectivity and washed ashore harmlessly."

That explosive claim, which set off alarms and triggered a tsunami of questions about Musk's role as a key figure potentially determining the fate of Vladimir Putin's ruthless war, turned out not to be quite as Isaacson had told it. Musk pushed back last week, writing on X that Starlink was never activated over Crimea and that he had actually received "an emergency request from government authorities" to enable the service, with the "obvious intent being to sink most of the Russian fleet at anchor."

"If I had agreed to their request, then SpaceX would be explicitly complicit in a major act of war and conflict escalation," Musk wrote.

Perhaps more importantly, Isaacson subsequently walked back the bombshell claim, which had received significant media coverage and was published as an "untold story" book excerpt in The Washington Post.

"To clarify on the Starlink issue: the Ukrainians THOUGHT coverage was enabled all the way to Crimea, but it was not," Isaacson posted on X, effectively reiterating what Musk had said. "They asked Musk to enable it for their drone sub attack on the Russian fleet."

"Based on my conversations with Musk, I mistakenly thought the policy to not allow Starlink to be used for an attack on Crimea had been first decided on the night of the Ukrainian attempted sneak attack that night," Isaacson added in a follow up post. "He now says that the policy had been implemented earlier, but the Ukrainians did not know it, and that night he simply reaffirmed the policy."

The correction has cast a pall over the biography from Isaacson, a highly respected author who has written acclaimed biographies on historic visionaries, including Steve Jobs, Benjamin Franklin, and Albert Einstein. Isaacson, a professor of history at Tulane University and former head of CNN, has for years enjoyed such a sterling reputation in the media industry that newsrooms have often taken his reporting to be fact.

Now, Isaacson is having to grapple with an embarrassing problem. A spokesperson for his publisher Simon & Schuster told me on Monday that "future editions of the book will be updated" to no longer include the error.

Newsrooms, meanwhile, are updating their stories in the wake of the mischaracterization. Over the weekend, The Post updated the excerpt it had published and offered a correction to its readers.

"After publication of this adaptation, the author learned that his book mischaracterized the attempted attack by Ukrainian drones on the Russian fleet in Crimea," the correction stated. "Musk had already disabled ('geofenced') coverage within 100 km of the Crimean coast before the attack began, and when the Ukrainians discovered this, they asked him to activate the coverage, and he refused. This version reflects that change."

CNN also updated its story on Monday, noting Isaacson had backpedaled his initial claims.

"After this story published, Walter Isaacson clarified his explanation regarding Elon Musk restricting Ukrainian military access to Starlink, a critical satellite internet service," an editor's note said. "This story has been updated to reflect that change."