It's been fashionable in military circles to talk about cyberspace as a "fifth domain" for warfare, along with land, space, air and sea. But there's a sixth and arguably more important warfighting domain emerging: the human brain.

This new battlespace is not just about influencing hearts and minds with people seeking information. It’s about involuntarily penetrating, shaping, and coercing the mind in the ultimate realization of Clausewitz’s definition of war: compelling an adversary to submit to one’s will. And the most powerful tool in this war is brain-computer interface (BCI) technologies, which connect the human brain to devices.

Chloe Diggins and Clint Arizmendi are research & analysis officers at the Australian army’s Land Warfare Studies Centre. The views expressed are their own and do not reflect those of the Australian Department of Defence or the Australian Government.

Current BCI work ranges from researchers compiling and interfacing neural data such as in the Human Conectome Project to work by scientists hardening the human brain against rubber hose cryptanalysis to technologists connecting the brain to robotic systems. While these groups are streamlining the BCI for either security or humanitarian purposes, the reality is that misapplication of such research and technology has *significant *implications for the future of warfare.

Where BCIs can provide opportunities for injured or disabled soldiers to remain on active duty post-injury, enable paralyzed individuals to use their brain to type, or allow amputees to feel using bionic limbs, they can also be exploited if hacked. BCIs can be used to manipulate ... or kill.

Recently, security expert Barnaby Jack demonstrated the vulnerability of biotechnological systems by highlighting how easily pacemakers and implantable cardioverter-defibrillators (ICDs) could be hacked, raising fears about the susceptibility of even life-saving biotechnological implants. This vulnerability could easily be extended to biotechnologies that connect directly to the brain, such as vagus nerve stimulation or deep-brain stimulation.

Outside the body, recent experiments have proven that the brain can control and maneuver quadcopter drones and metal exoskeletons. How long before we harness the power of mind-controlled weaponized drones – or use BCIs to enhance the power, efficiency, and sheer lethality of our soldiers?

>This new battlespace is not just about influencing hearts and minds. It’s about involuntarily penetrating and coercing the mind.

Given that military research arms such as the United States’ DARPA are investing in understanding complex neural processes and enhanced threat detection through BCI scan for P300 responses, it seems the marriage between neuroscience and military systems will fundamentally alter the future of conflict.

And it is here that military researchers need to harden the systems that enable military application of BCIs. We need to prevent BCIs from being disrupted or manipulated, and safeguard against the ability of the enemy to hack an individual’s brain.

The possibilities for damage, destruction, and chaos are very real. This could include manipulating a soldier’s BCI during conflict so that s/he were forced to pull the gun trigger on friendlies, install malicious code in his own secure computer system, call in inaccurate coordinates for an air strike, or divulge state secrets to the enemy seemingly voluntarily. Whether an insider has fallen victim to BCI hacking and exploits a system from within, or an external threat is compelled to initiate a physical attack on hard and soft targets, the results would present major complications: in attribution, effectiveness of kinetic operations, and stability of geopolitical relations.

Like every other domain of warfare, the mind as the sixth domain is neither isolated nor removed from other domains; coordinated attacks across all domains will continue to be the norm. It’s just that military and defense thinkers now need to account for the subtleties of the human mind ... and our increasing reliance upon the brain-computer interface.

Regardless of how it will look, though, the threat is real and not as far away as we would like – especially now that researchers just discovered a zero-day vulnerability in the brain.

Wired Opinion Editor: Sonal Chokshi @smc90