ROBERT OPPENHEIMER, the father of America’s nuclear bomb, described his country’s atomic rivalry with the Soviet Union as “two scorpions in a bottle”. The risks of this standoff have been contained over the years by various arms-control agreements, most recently New START. But that treaty expires on February 5th, with no replacement—and to make matters more dangerous, these days there is a third scorpion in the bottle: China. Its nuclear build-up, the world’s fastest since the height of the cold war, is likely to spur a response from America. A new arms race beckons.
When Xi Jinping, China’s leader, came to power in 2012, his country had only about 240 warheads, a fraction of the 1,550 both America and Russia were allowed to keep primed on long-range launch vehicles under New START. American military planners assumed that in a nuclear war with China, America’s vastly bigger arsenal would allow it to prevail in almost any scenario. But China now has some 600 warheads and is on track to reach 1,000 or more by 2030, according to the latest American estimates.
China still likes to boast of its “utmost restraint” in nuclear matters. After all, if you include warheads kept in storage, rather than ready to use, America and Russia both have more than 5,000. China “never has and never will engage in any nuclear arms race with any other country”, proclaims a recent policy paper. But the country has nonetheless developed the capacity to strike America with nuclear arms from the air, land and sea. A minutely choreographed military parade last year showed off these weapons, including a missile so enormous it had to be transported in three sections.
America has been unable to increase its nuclear arsenal in response while New START remains in force. Perhaps for that reason, it shows little regret at the treaty’s impending expiry. Russia says the end of restrictions on nuclear weapons should “alarm everyone” and recently suggested that both sides abide by New START’s limits voluntarily for another year. Some arms-control advocates hope that Donald Trump, America’s president, might come around to this idea, even after the treaty lapses. But he seems indifferent: “If it expires, it expires,” he said last month.
American planners are worried about a war with both China and Russia. America and its allies must be “prepared for the possibility that…potential opponents might act together in a co-ordinated or opportunistic fashion across multiple theaters”, declares the recent national-defence strategy. That is “an existential challenge for which the United States is ill-prepared”, a bipartisan commission created by Congress concluded in 2023. China and Russia increasingly make common cause, exchanging sensitive technology and conducting joint military exercises, sometimes with nuclear bombers. America’s current nuclear forces were not designed with China in mind, since it was considered a minor threat compared with Russia. The expansion of China’s nuclear capabilities undermines that assumption.
Phillip Saunders of National Defence University, an American military college, notes that China’s nuclear forces are undergoing several changes: they are not only growing larger, but also becoming more diverse, with multiple types of warheads and launchers. They are being placed on higher alert. And they are becoming more capable of what the Pentagon calls “launch on warning” (ie, to detect an attack and strike back before the enemy’s weapons arrive).
The Pentagon’s latest assessment notes that new satellites to detect missile launches and phased-array radars able to track them can alert Chinese commanders to an attack within 3-4 minutes. China’s armed forces are also better able to launch quick retaliatory strikes. Missiles in silos, loaded with solid fuel (rather than volatile liquid which cannot be stored in the missile), offer the fastest response. China has deployed about 100 in three vast fields of silos, designed to house up to 320 missiles, the Pentagon says. The country’s rocket forces have been rehearsing, too. In 2024 they fired a nuclear-capable missile 11,000km into the Pacific ocean. Three months later they fired several missiles in quick succession towards western China.
Experts debate why Mr Xi has ordered so fast a build-up. Mr Saunders thinks he is pursuing three overlapping aims. First, he wants a nuclear arsenal able to survive any American strike, giving him an assured second-strike capability. Although that typically involves putting missiles on hard-to-find submarines and mobile launchers, a proliferation of silos offers a cheap and quick way for China to beef up its arsenal.
Second, China may want a more flexible arsenal, capable of less cataclysmic uses than all-out nuclear war. The Pentagon reckons that China is developing small warheads, with yields below ten kilotons (as opposed to the 400 or more of those mounted on big intercontinental missiles). They could be placed on intermediate-range missiles, such as the DF-26, and used against America’s big bases in Guam if, say, America used similar, small nukes in a last-ditch attempt to save Taiwan from a Chinese invasion (the DF-26’s nickname is “Guam killer”).
Or Mr Xi may simply see a big nuclear arsenal as an emblem of “great-power status”. China already has more nuclear weapons than any country bar Russia and America (see chart). Does it want parity with their 5,000 or more warheads? Mr Saunders thinks China may aim for a “sweet spot” in between, to show China is a great power but a responsible one.
China claims it would not be the first to use nuclear weapons, but the doctrine is fuzzy, says Tong Zhao of the Carnegie Endowment for International Peace, a think-tank in Washington, DC. It could threaten to use nuclear weapons, as Russia has done in Ukraine. Or it could fire a warning shot over the ocean, or set off high-altitude detonations to destroy satellites. “If China is facing ugly and catastrophic conventional defeat, no one can rule out that it might decide to use nuclear weapons first,” says Mr Zhao. “Ultimately the authority rests with one person only.”
If China’s motives are uncertain, so is America’s response. A recent paper by the Heritage Foundation, a think-tank, calls for it to more than double total deployed warheads from about 1,770 to 4,625 by 2050. Others think that America already has more than enough survivable nuclear weapons to inflict devastating damage on both Russia and China, though it might have to abandon the idea of destroying enough of the enemy’s weapons to limit harm to America and its allies.
Vipin Narang, an official from Joe Biden’s administration, suggests a more modest deployment of up to 500 additional nuclear weapons, mainly to aim at China’s new silos. “There is no magic number. It all depends on how much risk you want to take,” he says. Franklin Miller, a former Pentagon nuclear planner, thinks about 300 would suffice.
Whatever the number, a build-up would be slow. America is already struggling to modernise all three legs of its nuclear triad, building new Sentinel land-based missiles, Columbia-class nuclear submarines and B-21 stealth bombers, as well as upgrading command-and-control systems. Some projects are woefully late or over budget.
For now, America can only “upload” extra warheads from reserves onto existing systems. It needs just days to put more air-launched cruise missiles into bombers, but months to install more warheads on missiles in nuclear submarines. It would take perhaps two years to convert the Minuteman III land-based missiles from one warhead each back to three. In 2023 the Federation of American Scientists, which monitors nuclear forces worldwide, calculated that America could deploy some 1,900 more warheads in these ways, compared with 1,000 for Russia. Expanding America’s total stockpile would take decades. If a nuclear arms-race went that far, Uncle Sam would be at a disadvantage: it can make only scores of new warheads a year whereas Russia can produce hundreds. However, Mr Miller points out that American planning is no longer based on cold-war notions of overkill, but on “sufficiency”: “If the Russians want to upload to make the rubble bounce, that’s their business.”
Whatever the pace of the new nuclear competition, the 40-year process of shrinking nuclear stockpiles is going into reverse. A more complex arms race than that of the cold war looms. China is already expanding its arsenal; if America builds up in response, Russia is certain to follow. India may feel compelled to counterbalance China, and Pakistan to offset India. Another source of instability is the fear that Mr Trump might abandon allies, which is prompting some of them to think about developing their own nukes. Recent American strategy documents, on national security and defence, say nothing about long-standing commitments to protect 30-odd allies and partners from nuclear attack. South Korea is especially worried. A Pentagon official who visited Seoul recently omitted to mention the threat from the nuclear-armed north. A world of relatively limited and known nuclear risks may soon become one of multiplying and unpredictable dangers.