Three alternatives to the current plan for nuclear-force modernisation would fulfil the principal function of the force: to deter a range of plausible threats from nuclear-armed rivals against the US and its allies.

The principal function of the US nuclear force is to deter a range of plausible threats from nuclear-armed rivals against the US and its allies. This objective is met by keeping high-value targets of potential nuclear adversaries constantly at risk, and by holding nuclear forces that are rapidly employable in a crisis, and able to survive an initial attack and then respond with devastating effect. Nuclear forces must also provide the US president with diverse options for responding to the threat or use of nuclear weapons. These options range from discriminate attacks on the military targets of the enemy that limit collateral damage, to massive attacks on urban areas and economic infrastructure. The US nuclear triad has maintained these attributes for decades. Each leg of the triad can independently deliver hundreds of nuclear weapons with a variety of explosive yields against protected or ‘hardened’ military targets as well as population centres and economic infrastructure.

US nuclear forces are not intended to threaten states that do not possess nuclear weapons, are party to the 1968 NPT and comply with their nuclear non-proliferation obligations. However, the 2010 NPR stated that the US ‘is not prepared at the present time to adopt a universal policy that deterring nuclear attack is the sole purpose of nuclear weapons, but will work to establish conditions under which such a policy could be safely adopted’. The language in the 2010 NPR was qualified in this manner because the US retains the right to use its nuclear weapons not simply for deterring nuclear attacks but also for possible pre-emptive nuclear attacks against potential adversaries. Two situations illustrate this possibility. Firstly, if the US concluded that an adversary was about to launch a nuclear attack on its territory or that of an ally, it could strike first with nuclear weapons in order to prevent that attack or limit the damage. Secondly, if US decision-makers determined that a nation possessing biological or chemical weapons was about to use them, a US pre-emptive nuclear strike could likewise be initiated.

Dr James E. Doyle formerly a specialist in the Nuclear Nonproliferation Division at Los Alamos National Laboratory, focuses on strategic planning and policy development in the field of nuclear weapons.

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