Donald Trump’s challenge to the taboo around nuclear weapons should worry us all

Moves to develop low-yield nuclear weapons for battlefield use could increase the danger of escalating conflict.

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Since their first devastating detonations in Hiroshima and Nagasaki, the use of nuclear weapons has been considered a taboo. Historically, US nuclear policy has aimed to ensure that these weapons are leveraged as part of a wider deterrence posture and their actual use would be limited to extreme conditions.

President Trump’s call for the development of new low-yield nuclear warheads challenges this policy and has led to concerns that the President is undermining the long-held taboo against the use of nuclear weapons. The recent reports on the draft Nuclear Posture Review (NPR) suggest that the US intends to expand the role of nuclear weapons and their potential use in the future. The review – if adopted in its current form – could stimulate a new arms race with Russia and further destabilize global security.

The current US nuclear policy relies on deterrence, which means persuading other states that the costs of military action against the US or its allies would be higher than the perceived benefits. But deterrence only works if states have a sufficient and similar level of understanding in regard to the enormous risks and a shared belief in deterrence postures. Efforts to increase the numbers and lower the threshold of use of nuclear weapons could paradoxically escalate the danger if they prompt other states to adopt similar measures.

In this instance, if the US decided to follow a nuclear approach based on the speedy deployment of low-yield nuclear weapons, this could be perceived as an existential threat to Russian nuclear forces, quite possibly leading Russia to react and develop even more new systems. An escalating, spiralling arms race that held the world to ransom during the Cold War was stabilised in large part through mutual and verifiable arms control – that lesson needs to be remembered.

Nuclear tensions are already escalating between Russia and the US. The US, for instance, identified the Russian violation of the Intermediate-range Nuclear Forces (INF) treaty in 2016 with the Russian cruise missile, Novator 9M729. Russia, however, has voiced concerns about the US’ modernisation programme. For instance, earlier last month, Mikhail Ulyanov, the Director of the Foreign Ministry Department for Non-Proliferation and Arms Control, stated that the B-61 modernisations (e.g. high accuracy) go beyond its purpose; making these weapons usable in the battlefield. The US modernisation also involves B61-12 bombs with earth-penetrating capability, which develops a new role and capacity for these bombers. Russia is also developing the new SARMAT missile (RS-28); its weight, the number of warheads it carries, and its speed, are all under question.

On the positive side, even though the suggested changes to the NPR are alarming, the reality is that the development of new nuclear capabilities will take years, even decades. The US Congress would need to put additional funds into the nuclear programme, which would require bipartisan consensus – one which may depend on new arms control and stabilisation negotiations with Russia.

One thing is clear: in developing new low-yield nuclear weapons, US nuclear policy would get closer to Russia’s nuclear strategy, which is to deescalate a conflict by actually escalating the military threats, including the possible limited use of nuclear weapons. This strategy is known as “escalate to de-escalate”.

Reframing the use of nuclear weapons in this way would be a great mistake – and one that has been made before. Instead, confidence-building measures, bilateral engagements, and verified de-escalation negotiations as part of a global nuclear non-proliferation leadership strategy is where the U.S. and Russia would be better focussing their resources and where, in the past, they have – individually and jointly – been effective and enjoyed considerable success.

Dr Beyza Unal is a research fellow in Nuclear Weapons Policy at the International Security Department of Chatham House.