It was Oct. 6, 2022, but what they heard instead that evening was a disturbing message that — though Mr. Biden didn’t say so — came straight from highly classified intercepted communications he had recently been briefed about, suggesting that President Vladimir V. Putin’s threats to use a nuclear weapon in Ukraine might be turning into an operational plan.
[...]
The intercepts revealed that for the first time since the war in Ukraine had broken out, there were frequent conversations within the Russian military about reaching into the nuclear arsenal. Some were just “various forms of chatter,” one official said. But others involved the units that would be responsible for moving or deploying the weapons. The most alarming of the intercepts revealed that one of the most senior Russian military commanders was explicitly discussing the logistics of detonating a weapon on the battlefield.
Fortunately, Mr. Biden was told in his briefings, there was no evidence of weapons being moved. But soon the C.I.A. was warning that, under a singular scenario in which Ukrainian forces decimated Russian defensive lines and looked as if they might try to retake Crimea — a possibility that seemed imaginable that fall — the likelihood of nuclear use might rise to 50 percent or even higher. That “got everyone’s attention fast,” said an official involved in the discussions.
[...]
“It’s the nuclear paradox,” Gen. Mark A. Milley, the chairman of the Joint Chiefs of Staff until he retired in September, told me over dinner last summer at his official quarters above the Potomac River, recalling the warnings he had issued in the Situation Room.
He added: “The more successful the Ukrainians are at ousting the Russian invasion, the more likely Putin is to threaten to use a bomb — or reach for it.”
[...]
Though the crisis passed, and Russia now appears to have gained an upper hand on the battlefield as Ukraine runs low on ammunition, almost all of the officials described those weeks as a glimpse of a terrifying new era in which nuclear weapons were back at the center of superpower competition.
While news that Russia was considering using a nuclear weapon became public at the time, the interviews underscored that the worries at the White House and the Pentagon ran far deeper than were acknowledged then, and that extensive efforts were made to prepare for the possibility. When Mr. Biden mused aloud that evening that “I don’t think there’s any such thing as the ability to easily” make use of “a tactical nuclear weapon and not end up with Armageddon,” he was reflecting urgent preparations being made for a U.S. reaction.
[...]
Yet as was made clear in Mr. Biden’s “Armageddon speech” — as White House officials came to call it — no one knew what kind of nuclear demonstration Mr. Putin had in mind. Some believed that the public warnings Russia was making that Ukraine was preparing to use a giant “dirty bomb,” a weapon that spews radiological waste, was a pretext for a pre-emptive nuclear strike.
The wargaming at the Pentagon and at think tanks around Washington imagined that Mr. Putin’s use of a tactical weapon — perhaps followed by a threat to detonate more — could come in a variety of circumstances. One simulation envisioned a successful Ukrainian counteroffensive that imperiled Mr. Putin’s hold on Crimea. Another involved a demand from Moscow that the West halt all military support for the Ukrainians: no more tanks, no more missiles, no more ammunition. The aim would be to split NATO; in the tabletop simulation I was permitted to observe, the detonation served that purpose.
To forestall nuclear use, in the days around Mr. Biden’s fund-raiser appearance Secretary of State Antony J. Blinken called his Russian counterpart, as did Defense Secretary Lloyd J. Austin III and the national security adviser, Jake Sullivan. Germany’s chancellor, Olaf Scholz, was going on a planned visit to Beijing; he was prepped to brief Xi Jinping, China’s president, about the intelligence and urge him to make both public and private statements to Russia warning that there was no place in the Ukraine conflict for the use of nuclear weapons. Mr. Xi made the public statement; it is unclear what, if anything, he signaled in private.
Mr. Biden, meanwhile, sent a message to Mr. Putin that they had to set up an urgent meeting of emissaries. Mr. Putin sent Sergei Naryshkin, head of the S.V.R., the Russian foreign intelligence service that had pulled off the Solar Winds attack, an ingenious cyberattack that had struck a wide swath of U.S. government departments and corporate America. Mr. Biden chose William J. Burns, the C.I.A. director and former U.S. ambassador to Russia, who is now his go-to troubleshooter for a variety of the toughest national security problems, most recently getting a temporary cease-fire and the release of hostages held by Hamas.
Mr. Burns told me that the two men saw each other on a mid-November day in 2022. But while Mr. Burns arrived to warn what would befall Russia if it used a nuclear weapon, Mr. Naryshkin apparently thought the C.I.A. director had been sent to negotiate an armistice agreement that would end the war. He told Mr. Burns that any such negotiation had to begin with an understanding that Russia would get to keep any land that was currently under its control.
It took some time for Mr. Burns to disabuse Mr. Naryshkin of the idea that the United States was ready to trade away Ukrainian territory for peace. Finally, they turned to the topic Mr. Burns had traveled around the world to discuss: what the United States and its allies were prepared to do to Russia if Mr. Putin made good on his nuclear threats.
“I made it clear,” Mr. Burns later recalled from his seventh-floor office at the C.I.A., that “there would be clear consequences for Russia.” Just how specific Mr. Burns was about the nature of the American response was left murky by American officials. He wanted to be detailed enough to deter a Russian attack, but avoid telegraphing Mr. Biden’s exact reaction.
