(CNN) — Elon Musk secretly ordered his engineers to turn off his company’s Starlink satellite communications network near the Crimean coast last year to disrupt a Ukrainian sneak attack on the Russian naval fleet, according to an excerpt adapted from Walter Isaacson’s new biography of the eccentric billionaire titled “Elon Musk.”

As Ukrainian submarine drones strapped with explosives approached the Russian fleet, they “lost connectivity and washed ashore harmlessly,” Isaacson writes.

Musk’s decision, which left Ukrainian officials begging him to turn the satellites back on, was driven by an acute fear that Russia would respond to a Ukrainian attack on Crimea with nuclear weapons, a fear driven home by Musk’s conversations with senior Russian officials, according to Isaacson, whose new book is set to be released by Simon & Schuster on September 12.

Musk’s concerns over a “mini-Pearl Harbor” as he put it, did not come to pass in Crimea. But the episode reveals the unique position Musk found himself in as the war in Ukraine unfolded. Whether intended or not, he had become a power broker US officials couldn’t ignore.

The new book from Isaacson, the author of acclaimed biographies of Steve Jobs and Albert Einstein, provides fresh insights into Musk and how his existential dread of sparking a wider war drove him to spurn Ukrainian requests for Starlink systems they could use to attack the Russians.

After Russia disrupted Ukraine’s communications systems just before its full-scale invasion in February 2022, Musk agreed to provide Ukraine with millions of dollars of SpaceX-made Starlink satellite terminals, which became crucial to Ukraine’s military operations. Even as cellular phone and internet networks had been destroyed, the Starlink terminals allowed Ukraine to fight and stay connected.

But once Ukraine began to use Starlink terminals for offensive attacks against Russia, Musk started to second-guess that decision.

“How am I in this war?” Musk asks Isaacson. “Starlink was not meant to be involved in wars. It was so people can watch Netflix and chill and get online for school and do good peaceful things, not drone strikes.”

Musk was soon on the phone with President Joe Biden’s national security adviser, Jake Sullivan, the chairman of the joint chiefs, Gen. Mark Milley, and the Russian ambassador to the US to address anxieties from Washington, DC, to Moscow, writes Isaacson.

Meanwhile, Mykhailo Fedorov, a deputy prime minister of Ukraine, was pleading with Musk to restore connectivity for the submarine drones by telling Musk about their capabilities in a text message, according to Isaacson. “I just want you—the person who is changing the world through technology—to know this,” Fedorov told Musk.

Musk and SpaceX did not reply to CNN’s requests for comment.