The US-Russia New START nuclear treaty expires this week. Will Trump and Putin renew it?

The Poseidon super-torpedo is a marvel of Russian engineering (if accounts are to be believed). A sinister black cylinder the length of a train carriage, weighing more than 100 tonnes and powered by its own on-board nuclear reactor, it can travel thousands of kilometres in deep water, virtually undetected. Equipped with a nuclear warhead, it can wipe out an aircraft carrier group or swamp a coastal city under a radioactive tsunami – apocalypse fiction made horrendously real.

“There is nothing like this,” Russian President Vladimir Putin boasted in October after what he claimed had been a successful test launch of the Poseidon from a submarine.

Some military analysts who have watched Poseidon’s development over the past decade suggest Russia’s claims are overblown. But if it can do even a fraction of what’s advertised and, as Russian media have reported, 30 of these giants are indeed ready for launch from four submarines as early as next year, Poseidon will add another scary dimension to the politics of global nuclear brinksmanship.

This is a particularly ominous development given the last remaining bilateral agreement between Russia and the United States limiting their stockpiles of nuclear warheads, long-range bombers and missiles, the New Strategic Arms Reduction Treaty (or New START), will expire on February 5.

Once it lapses, Russia and the US will again be free to expand their nuclear capacity unencumbered. Observers tell us they expect both superpowers to ramp up their numbers of usable warheads by constructing new ones (for the likes of Poseidon) and bringing previously mothballed stocks out of storage.

“It’s potentially very bleak for nuclear risk and arms control,” says Tilman Ruff, founding chair of the International Campaign to Abolish Nuclear Weapons, which was awarded the Nobel Peace Prize in 2017. “At this point, you’d have to say it looks like we’re in a completely new world where there are no treaty constraints on the two biggest arsenals in the world from February, which is an extraordinary position.”

China, meanwhile, has become the world’s third major nuclear force, leapfrogging India, Pakistan, Britain and France, who have close to 1000 warheads between them. Then there’s North Korea (which brags about its capacity), Israel (which obscures it) and the dozens of nations that don’t have nuclear weapons but, thanks to their civilian reactors, theoretically have the capacity to develop them. “We’re definitely in an era again where nuclear weapons are much more central to national survival than we’ve seen in the past,” says Professor Stephan Fruehling at ANU’s Strategic and Defence Studies Centre in Canberra.

Oppenheimer, who directed the secret laboratory that developed the World War II US nuclear program, was subsequently among the first to call for international agreements to avoid an arms race.

Since the dawn of the nuclear age, there have been efforts to limit nuclear proliferation. Robert Oppenheimer, who directed the secret laboratory that developed the World War II US nuclear program, was subsequently among the first to call for international agreements to avoid an arms race and argued loudly against the development of the hydrogen bomb (a massively more powerful weapon than those used in WWII, first exploded by the US in 1952 at Enewetak Atoll in the Marshall Islands).

An early milestone was the Antarctic Treaty of 1959, when Argentina, Australia, Belgium, Britain, Chile, France, Japan, New Zealand, Norway, South Africa, the Soviet Union and the United States agreed to keep the glacial continent demilitarised and, expressly, free from nuclear testing. Another breakthrough was the 1963 “hotline” agreement that established a direct link between the US and Soviet heads of state to (hopefully) avoid a nuclear exchange triggered by an accident or misunderstanding (although it wasn’t a red telephone in the Oval Office, as the movies would have it, but rather a visually less interesting but more reliable text-based system).

Then there were the “SALT” talks in the late 1960s that led to two major agreements in 1972, known as SALT I, the first substantive effort by the US and the USSR to limit their strategic arms, in this case land- or submarine-based nuclear missiles as well as limits on rockets to counter incoming missiles, a key component of the calculus of deterrence. (“Strategic” in this context means weapons capable of crossing continents; shorter-range “tactical” weapons are employed on battlefields against armies and have been subject to a separate agreement.)

Broader international agreements have generally proved harder to get over the line. While the US, Britain and the USSR signed the Limited Test Ban Treaty in 1963, prohibiting explosions underwater, in the atmosphere and space, France didn’t, instead testing above ground in the South Pacific until 1974, and underground there until 1996; its 46 atmospheric tests around Mururoa Atoll contaminated 110,000 local people with radioactive fallout, according to a 2021 study. China joined the nuclear club in 1964 but declined to sign the 1963 treaty and continued atmospheric testing until 1980.

The Nuclear Non-Proliferation Treaty of 1968 tried to limit nuclear weapons to the “first five” – the US, USSR, Britain, France and China – with an eventual goal of disarmament, in exchange for supplying other nations with the technology to build civilian nuclear power plants. Today 191 states have joined. Not among them: Israel (believed to have developed its first bomb in 1967), nuclear rivals India and Pakistan and nuclear state North Korea, which withdrew in 2003.

‘The idea is that over time, more and more states will join such a treaty, and this puts moral pressure on the nuclear states to exercise restraint and move to disarmament.’

A similarly ambitious United Nations agreement brought into force in 2021, the Treaty on the Prohibition of Nuclear Weapons (TPNW), makes it illegal for signatories to develop, test, produce, manufacture, acquire, possess, stockpile, transfer, use or threaten to use nuclear weapons, but none of the nine known nuclear states has yet joined it so are not beholden to its rules. Australia, which has no nuclear weapons but exports uranium and is a strong ally of the US, hasn’t signed either, though Labor’s national policy platform has since 2018 committed Labor in government to join the treaty, according to Ruff. Foreign Minister Penny Wong said in 2023 that the Labor government was “considering the TPNW systematically and methodically as part of our ambitious agenda to advance nuclear non-proliferation and disarmament”.

Nevertheless, the TPNW treaty still has a valuable social context, argues Marianne Hanson, an expert in international relations at the University of Queensland. “The idea is that over time, more and more states will join such a treaty, and this puts moral pressure on the nuclear states to exercise restraint and move to disarmament.”

The soon-to-expire New START agreement always came with a use-by date. Signed after tortuous backroom negotiations by US and Rus­sian pres­i­dents Barack Obama and Dmitry Medvedev in a time of relative stability in 2010, and coming into force in 2011, it was only ever to last a maximum of 15 years (10 plus a one-off extension of up to five years agreed by Joe Biden and Putin in January 2021). A sign of the times: Medvedev was optimistic it would lead to ever greater co-operation. “I wouldn’t like to see the Russian Federation and the United States be narrowed down to just limiting strategic offensive arms,” he told Obama.

More recently, Putin has informally proposed both sides stick to the rules for another 12 months but nothing official has been agreed. In January, Trump suggested to The New York Times he was prepared for New START to lapse, saying, “When they negotiated that agreement, they didn’t do a very good job … I’d rather do a new agreement that’s much better.”

China’s ascent to the nuclear top table will complicate any future agreements, analysts say. It is now believed to have some 600 warheads and the capacity to deliver them by land-based and submarine-fired missiles and jet bombers, the so-called impregnable “nuclear triad”. Trump told The New York Times, “China should be a part of the agreement … I spoke to President Xi [Jinping] about it previously, and I think he’d be a willing participant … I would do a deal with Russia without the Chinese. But I think … that China would be a good participant in a deal.” (Pavel Podvig, a senior researcher at the UN’s weapons of mass destruction program, is less optimistic: “China is not interested.” )

Both the US and Russia are believed to have met the New START requirement that they cap their stockpiles of strategic nuclear warheads at 1550 each and also to limit the numbers of deployed missiles and heavy bombers to 700. The treaty did not, however, limit warheads attached to short and intermediate-range missiles – which were covered by the bilateral Intermediate-Range Nuclear Forces or “INF” treaty, signed by Russian leader Mikhail Gorbachev and US president Ronald Reagan in 1987 and now defunct – nor warheads in long-term storage, which bring the total ultimately available warheads to some 5000 for each nation.

Critically, for much of the duration of New START, both sides also agreed to a rigorous program of monitoring and inspections. “All of that helps to reduce nuclear risk, keep communication lines open, improve stability and confidence in a crisis,” says Ruff. “You know who to talk to. You know what they’re doing. You know that this exercise, or these rockets being moved from here to there, isn’t the start of an attack.”

‘Clearly, there’s no transparency any longer, and transparency and developing trust and confidence-building measures is a really, really strong part of all arms control agreements.’

That communication began to break down during COVID, which restricted the capacity to conduct on-site inspections, and thanks to the war in Ukraine, says Hanson, who is also a co-chair of the International Campaign to Abolish Nuclear Weapons. “Clearly, there’s no transparency any longer, and transparency and developing trust and confidence-building measures is a really, really strong part of all arms control agreements.” (According to the Chatham House think tank, Putin suspended Russia’s active participation in the treaty in 2023, followed by the US. Both sides signalled they would stick to the treaty’s weapons caps.)

America has not tested nuclear weapons since 1992 but, in October, Trump suggested on social media that the US should do so (though it wasn’t clear whether he meant actual explosions or tests of delivery systems). Putin’s forces, meanwhile, have started to use weapons that fall outside the scope of agreements, such as the Oreshnik hypersonic missile that struck the Ukrainian city of Lviv on January 10. Hypersonic missiles can carry a nuclear warhead (though that one didn’t), reach speeds of 13,000km/h over long distances and change course quickly, making them near-impossible to intercept – complicating the role that anti-missile systems play in deterrence and treaty negotiations.

Iran may yet ramp up its nuclear program, giving regional foes such as Saudi Arabia cause to consider their own plans to join the nuclear club, as might Japan and South Korea, long considered “nuclear-latent” states with the technology and expertise to develop nuclear weapons quickly. Artificial intelligence could make weapons development easier and faster.

The stakes could not be higher. Even a so-called limited nuclear exchange between, say, India and Pakistan – which came to blows as recently as 2025 over Kashmir – would throw enough soot into the atmosphere to plunge the globe into a nuclear winter, causing crop failures and starving billions, Ruff tells us.

‘How many do you need? Two, three, five, 10? You don’t need thousands.’

While the US is pursuing a trillion-dollar program to update and replace ageing missiles and bombers and Russia boasts of weapons breakthroughs, in practical terms they are hampered somewhat by resources, says Podvig, pointing to both nations’ limited industrial capacity after years of allowing their nuclear infrastructure to run down. Surely, though, even the 1550 strategic warheads each that Russia and the US have operational already would be sufficient? Certainly, says Ruff: “How many do you need for deterrence? Two, three, five, 10? You don’t need thousands. You would have them on a platform that was invulnerable to attack and detection. These days, on a submarine.”

This is where we get into the game theory of deterrence, now even more complicated by the US potentially facing not one but two major foes. Says Fruehling: “If you find yourself in a nuclear conflict with one, you want to make sure that you have enough left over to deter the other – that’s basically the argument behind this. There are good arguments that the Americans will increase numbers.”

It was not a surprise, then, that on January 27, the Bulletin of the Atomic Scientists, founded by scientists and engineers of the Manhattan Project in the wake of the atomic bombings of Hiroshima and Nagasaki, declared it had moved the hands of its famous “Doomsday Clock” forward to 85 seconds to midnight, the closest it has ever been to indicating looming annihilation. Says Hanson: “The analysts who do this, they base their research on bilateral relations between various nuclear states, the imminent collapse of New START treaty, increasing hostile rhetoric. So it’s all moving the wrong direction.”

Bottom line, says Ruff: “We’re in a really alarming situation of multiple arms races accelerating. We’re seeing no disarmament negotiations under way. We’re seeing nuclear-armed states actively involved in wars, making nuclear threats. We’re seeing attacks on sovereign states, including by nuclear-armed states. We know that nuclear command-and-control systems are vulnerable to cyberattack, and we’re on the cusp of applications of artificial intelligence in military systems, including nuclear command-and-control systems, before we’ve really even understood the implications and risks. So it’s a pretty comprehensively alarming nuclear risk landscape.”

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