As several participants in our debate have argued, nuclear ballistic missile submarines (SSBN) can have a positive effect on strategic stability in Asia and globally. But they do not exist in a vacuum. New military capabilities, and strategies that take advantage of them, are being developed and deployed in the Indo-Pacific that make the gradual proliferation of sea-based nuclear weapons dangerous rather than stabilising. 

These novel weapons, such as cyber and electronic warfare, anti-satellite missiles and hypersonic technology, add new dimensions to both conventional warfare and nuclear deterrence. Their development, along with their roles in comprehensive strategies, such as the US’s Air-Sea Battle concept, requires us to ask whether the introduction of Chinese and Indian sea-launched nuclear weapons will only create instability and the risk of escalation in conflict. 

The role of SSBNs is to provide an assured second-strike capability to a nation's nuclear deterrence. Essentially, a second strike capability acts as a kind of fail-safe by ensuring that any aggressor takes on the risk of being attacked by nuclear weapons in-kind. Thus, theoretically, SSBNs and assured second strike should lead to a more stable strategic system in the Indo-Pacific by deterring any potential disabling first strike.

As Rod Lyon has argued, the SSBN can make an aggressor think twice, as long as the threat of the platform is credible. It is mobile, quiet and difficult to track. Once professional crews, reliable communication technology and effective command and control are established, the SSBN can act as a credible deterrent. But if the SSBN is to play a positive role in strategic stability, communication with state leadership must be guaranteed. 

Communications with submerged submarines, both conventional and nuclear, are established through very low frequency and extremely low frequency programs. These involve large antenna installations that are part of a state's military communications network. Thus for example India, conducting sea-trials of its first SSBN, has started construction of its own very low frequency station

But what happens to deterrence and stability if such communications come under attack?

In the Cold War, the main way to neutralize an adversary's submarine-launched nuclear weapons was through anti-submarine warfare; detecting and tracking enemy SSBNs and, in the event of war, destroying them before they launched. 

There was, of course, the risk that during a conflict anti-submarine warfare could induce 'use it or lose it' decisions on a state's leadership. That destabilising factor is now amplified by another possibility raised by new technologies: the prospect that a state's communications with its nuclear deterrent force could be cut in times of crisis.

What would happen in a future conflict in which the opening attack involved the use of cyber and other capabilities to disrupt or destroy military communication systems? How could we be certain that SSBN commanders, cut off from political authority, would not launch their weapons? 

This goes to wider questions about vulnerability of communications, including satellites, in conflict. The head of US Air Force Space Command recently said that if one of the Advanced Extremely High Frequency satellites, a backbone of US military communication, was taken out 'we could potentially have a situation where the president can't communicate with forces in that part of the world.'

There is no guarantee that striking another power blind or dumb in the midst of crisis would add to stability. Thus the US Air-Sea Battle concept has an uneasy relationship with nuclear deterrence. Designed to counter Chinese anti-access and area-denial capabilities, Air-Sea Battle requires the integration of all 'interdependent warfighting domains (air, maritime, land, space and cyberspace)' in order to 'disrupt, destroy and defeat' enemy forces. The strategy calls for the disruption of enemy 'command, control, communication, computers, intelligence, surveillance and reconnaissance' systems before attacking their weapon systems and capabilities.

Many of these communication systems, like the low frequency installation India is building, are dual-use in the sense that they could network with conventional and nuclear forces. Thus it is possible to foresee a situation where a 'blinding' campaign like that envisioned in Air-Sea Battle could involve attacks on an installation that also communicates with SSBNs, radically disrupting a state's control over its sea-based nuclear arsenal. Presumably, India would face a similar problem if Pakistan or China ever planned to target its communications at the outset of a conflict.

These are some of the complexities and scenarios that will need to be thought through if the introduction of Chinese and Indian nuclear-armed submarines is to reduce risks of conflict rather than heighten them.

The Lowy Institute gratefully acknowledges support from the John D and Catherine T MacArthur Foundation for this Interpreter debate, which is part of a broader research, dialogue and outreach project on strategic stability in Indo-Pacific Asia.

Photo courtesy of Flickr user U.S. Navy Official Page