The risk of
nuclear conflict
is rising.

Nuclear nations are
building up their arsenals,
speeding toward
the next arms race.

Is anyone
paying attention?

Today’s generation of weapons — many of which are fractions of the size of the bombs America dropped in 1945 but magnitudes more deadly than conventional ones — poses an unpredictable threat.

It hangs over battlefields in Ukraine as well as places where the next war might occur: the Persian Gulf, the Taiwan Strait, the Korean Peninsula.

This is one story of what’s at stake — if even one small nuclear weapon were used — based on modeling, research and hundreds of hours of interviews with people who have lived through an atomic detonation, dedicated their lives to studying nuclear war or are planning for its aftermath.

Nuclear war is often described as unimaginable. In fact, it’s not imagined enough.

If it seems alarmist to anticipate the horrifying aftermath of a nuclear attack, consider this: The United States and Ukraine governments have been planning for this scenario for at least two years.

In the fall of 2022, a U.S. intelligence assessment put the odds at 50-50 that Russia would launch a nuclear strike to halt Ukrainian forces if they breached its defense of Crimea. Preparing for the worst, American officials rushed supplies to Europe. Ukraine has set up hundreds of radiation detectors around cities and power plants, along with more than 1,000 smaller hand-held monitors sent by the United States.

Nearly 200 hospitals in Ukraine have been identified as go-to facilities in the event of a nuclear attack. Thousands of doctors, nurses and other workers have been trained on how to respond and treat radiation exposure. And millions of potassium iodide tablets, which protect the thyroid from picking up radioactive material linked with cancer, are stockpiled around the country.

But well before that — just four days after Russia launched its invasion of Ukraine, in fact — the Biden administration had directed a small group of experts and strategists, a “Tiger Team,” to devise a new nuclear “playbook” of contingency plans and responses. Pulling in experts from the intelligence, military and policy fields, they pored over years-old emergency preparedness plans, weapon-effects modeling and escalation scenarios, dusting off materials that in the age of counterterrorism and cyberwarfare were long believed to have faded into irrelevance.

The playbook, which was coordinated by the National Security Council, now sits in the Eisenhower Executive Office Building, next to the West Wing of the White House. It has a newly updated, detailed menu of diplomatic and military options for President Biden — and any future president — to act upon if a nuclear attack occurs in Ukraine.

At the heart of all of this work is a chilling conclusion: The possibility of a nuclear strike, once inconceivable in modern conflict, is more likely now than at any other time since the Cold War. “We've had 30 pretty successful years keeping the genie in the bottle,” a senior administration official on the Tiger Team said. While both America and Russia have hugely reduced their nuclear arsenals since the height of the Cold War, the official said, “Right now is when nuclear risk is most at the forefront.”

Russian President Vladimir Putin reminded the world of this existential danger last week when he publicly warned of nuclear war if NATO deepened its involvement in Ukraine.

President Vladimir Putin, February 2024

The risk of nuclear escalation in Ukraine, while now low, has been a primary concern for the Biden administration throughout the conflict, details of which are being reported here for the first time. In a series of interviews over the past year, U.S. and Ukrainian officials spoke on condition of anonymity to discuss internal planning, diplomacy and ongoing security preparations.

And while it may cause sleepless nights in Washington and Kyiv, most of the world has barely registered the threat. Perhaps it’s because an entire generation came of age in a post-Cold War world, when the possibility of nuclear war was thought to be firmly behind us. It is time to remind ourselves of the consequences in order to avoid them.

Even after last week’s nuclear threat, few believe that Mr. Putin will wake up one day and decide to lob megaton warheads at Washington or European capitals in retaliation for supporting Ukraine. What Western allies see as more likely is that Russia will use a so-called tactical nuclear weapon, which is less destructive and designed to strike targets over short distances to devastate military units on the battlefield.

The strategic thinking behind those weapons is that they are far less damaging than city-destroying hydrogen bombs and therefore more “usable” in warfare. The United States estimates Russia has a stockpile of up to 2,000 tactical........

© The New York Times