A staffer handed him an iPhone—in part to avoid inviting an onslaught of late-night texts and colorful emojis on Kahl's own phone. Kahl had returned to his room, with its heavy drapery and distant view of the Eiffel Tower, after a day of meetings with officials from the United Kingdom, France, and Germany. A senior defense official told me that Kahl was surprised by whom he was about to contact: "He was, like, 'Why am I calling Elon Musk?' "

The reason soon became apparent. "Even though Musk is not technically a diplomat or statesman, I felt it was important to treat him as such, given the influence he had on this issue," Kahl told me. SpaceX, Musk's space-exploration company, had for months been providing Internet access across Ukraine, allowing the country's forces to plan attacks and to defend themselves. But, in recent days, the forces had found their connectivity severed as they entered territory contested by Russia. More alarmingly, SpaceX had recently given the Pentagon an ultimatum: if it didn't assume the cost of providing service in Ukraine, which the company calculated at some four hundred million dollars annually, it would cut off access. "We started to get a little panicked," the senior defense official, one of four who described the standoff to me, recalled. Musk "could turn it off at any given moment. And that would have real operational impact for the Ukrainians."