There are three main reasons we advocate strongly for concerted activity towards a global ban on these nuclear weapons. They are instruments of a significant reduction in Nuclear Strategic Stability.
Nuclear Cruise Missiles Weaken Deterrence
A ballistic missile is instantly recognisable on launch, whether from a land or sea based location. Launched by a state owning nuclear weapons such a launch will be classified immediately as a nuclear weapon launch. There is no risk of miscalculation, and a suitable response is inevitable, therefore the launching state will not launch except in the most extreme circumstances indicated in its declaratory policy. That certainty and implacability delivers strategic deterrence.
Conventional cruise missiles abound in air- land- or sea-launched versions. A nuclear-capable state which has a nuclear variant of any of its cruise missiles immediately risks miscalculation. A cruise missile launch from such a state could be conventional; equally it could be nuclear. There is no way of knowing with dual use weapons.
The fact that cruise missiles have been regularly used in the last 25 years with no emergent miscalculation is often cited as a rationale for these weapons not to be destabilising. This is misleading. Miscalculation will only occur when launching a cruise missile from a nuclear weapons state towards or in the vicinity of another nuclear weapons state.
Nuclear Cruise Missiles Risk a Reduction in Threshold of Use
The presence of nuclear cruise missiles in a nuclear weapon states arsenal immediately signals that the state is contemplating the employment of nuclear weapons at a less than strategic level.
Whether or not the state considers within its declaratory policy that these weapons exist jointly to offer choice to the national leadership in a strategic crisis, these weapons have clear utility at the operational and tactical level during a conflict.
By delivering a less than strategic employment of nuclear weapons, and particularly if the target area is not within the national boundaries of the nuclear armed adversary, the acceptability of employment of these weapons is increased, thresholds are lowered, and risk is significantly increased.
In addition, the re-emerging perception – particularity in Washington and Moscow – that the use weapons have military utility at a lower level in the spectrum of conflict risks a less than strategic threshold of use.
Nuclear Cruise Missiles Weaken Non Proliferation Efforts
For nuclear weapon states with sufficient strategic nuclear capability to assure deterrence against a major nuclear attack, the maintenance of a nuclear cruise missile capability and continued assertion that these weapons are an essential component of successful deterrence severely weakens any non-proliferation message.
The most established nuclear weapons states, and particularly those in the west, set great store in all-arms control and counter proliferation activity as functioning elements in the National Security policy. Both the Nuclear non-Proliferation Treaty and the Missile Technology Control Regime are key components of that activity. But without setting an example, these are severely weakened.
Proliferation of these weapons and the perception that the only deterrence against them is fielding a similar capability risks a new nuclear cruise missile arms race.