Three days into 2022, the world’s top nuclear powers issued a joint statement declaring that their city-busting weapons were no longer aimed at one another and reaffirming their post-Cold War commitment to avoiding an apocalyptic Third World War. “We affirm that a nuclear war cannot be won and must never be fought,” said the U.S., China, France, Britain and Russia. “As nuclear use would have far-reaching consequences, we also affirm that nuclear weapons—for as long as they continue to exist—should serve defensive purposes, deter aggression, and prevent war.”

On Sunday, less than two months later, Russian President Vladimir Putin abandoned the spirit of that pledge, publicly directing Russia’s nuclear forces to go on a high alert status following his Feb. 24 invasion of neighboring Ukraine. Facing unexpected resistance from Ukrainians and global condemnation for the unprovoked assault, Putin said in a televised meeting with his two top military officials that he was putting the military on a “special combat readiness,” in response to what he called “aggressive statements” by the U.S. and its European allies.
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The announcement appeared to be primarily for show, coming ahead of expected talks between Russian and Ukrainian officials. U.S. government and independent analysts said it brought no immediate change in the status of Russia’s strategic arsenal. But the nuclear saber-rattling reminded the world that any crisis, no matter how big or small, holds the potential for catastrophic consequences when nations armed with thermonuclear arsenals are involved. The Biden Administration now must determine how to avoid escalation with Russia while also maintaining deterrence and pressure on the Kremlin in coordination with North Atlantic Treaty Organization (NATO) allies.

Read More: Russia’s Invasion of Ukraine Is a Major Test for Joe Biden’s Foreign Policy Vision

The U.S. and the rest of NATO have stayed out of the fighting in Ukraine, but in recent days they have increased military aid to the former Soviet-bloc nation as it faces a daily Russian onslaught from the air, land and sea. The White House and the European Union have also implemented a sweeping package of economic sanctions that targets Russia’s financial institutions, major enterprises and individuals in Putin’s power hierarchy. Putin’s nuclear forces order came less than 24 hours after the most severe sanctions were announced.

“We believe this is not only an unnecessary step for him to take, but an escalatory one,” said a senior U.S. defense official, who was not authorized to speak publicly on the matter. “It’s unnecessary because Russia has never been under threat by the West or by NATO. It is escalatory because it’s potentially putting in play forces that that could—if there’s a miscalculation—make things much more dangerous.”

From a tactical perspective, it remains unclear what change, if any, Putin has effected with the order. U.S. intelligence had yet to see any operational changes on how Russia’s nuclear triad of bombers, submarines, and missiles were postured, the defense official said. “We have no reason to doubt the validity of this order, but how it’s manifested itself, I don’t think is completely clear yet,” the official said.

Jeffrey Lewis, an analyst with the James Martin Center for Nonproliferation Studies Middlebury Institute of Strategic Studies, said many of Russia’s nuclear forces are already on day-to-day alert so this could be Putin’s way of turning on certain command-and-control systems or simply raising the readiness of his forces—or it could all be for show. “The fact that he announced it, however, leads me to think he’s just a big peacock-spreading his feathers,” Lewis says.

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Olga Oliker, the International Crisis Group’s director for Europe and Central Asia, said there are a variety of reasons why Putin might have made the nuclear declaration. These include his desire to dissuade the Western powers from continuing to support Ukraine or his need for leverage in the upcoming cease-fire negotiations with Ukraine. Either way, it looks like an act of desperation by a man running out of cards to play. “Presumably, none of these would be issues if the military operation was going better for Russia,” Oliker said.

The Russian advance in Ukraine is going slower than U.S. intelligence anticipated, the senior defense official said, with the military incurring logistics problems and Ukrainian forces giving them stiff resistance. No major Ukrainian city has yet fallen to Moscow. Airspace over Ukraine remains contested, despite predictions that Russian fighter jets would quickly dominate the skies.

The Pentagon said the Russian military has resorted to siege tactics around the city of Chernihiv, located northeast of the capital Kyiv. After launching more than 320 missiles, most of them short-range, the forces are now also lobbing unguided rockets to reach targets. This is expected to raise the number of civilian casualties. “We don’t know if it’s a failure in planning or a failure in execution,” the official said.

Elsewhere, Russian missiles hit the site of a radioactive waste disposal facility in Kyiv. A day before, an electrical transformer was damaged at a nuclear waste disposal facility near Ukraine’s second largest city, Kharkiv. There was no indication of radioactive release, according to the International Atomic Energy Agency. “These two incidents highlight the very real risk that facilities with radioactive material will suffer damage during the conflict, with potentially severe consequences for human health and the environment,” Agency Director General Rafael Grossi said.

No nation has detonated a nuclear weapon in conflict since the U.S. dropped atomic bombs in 1945 on the Japanese cities of Hiroshima and Nagasaki. After the runaway arms race of the Cold War, Russia and the U.S. arsenals are now capped at 1,550 deployed nuclear warheads under a bilateral treaty known as New START. Both countries, however, have hundreds of smaller tactical weapons that are designed for limited battlefield use.

The Pentagon refused to comment Sunday on whether the alert status of U.S. nuclear forces had changed due to Putin’s announcement. The U.S. maintains a vast intelligence network of sensors and overhead surveillance to catch any signs that Russian strategic elements have changed their nuclear posture on the ground. If forces begin to arm bombers or ready missiles, a constellation of school bus–sized satellites will likely capture the deviations.

The lack of apparent movement by Russian strategic forces was only marginally reassuring, however, to some experienced observers watching the escalating war in Ukraine. One former U.S. official saw in Putin’s comments an alarming shift in rhetoric concerning the world’s most powerful weapons. “If you hold up a store armed with a gun, you’ll be charged with armed robbery,” the former official said. “What Putin did today was nuclear-armed robbery.”