Alan Kearney | 02.04.26
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A few months ago, during a closed-door seminar involving senior officials in the United States defense community, I raised a concern about the direction of night-vision modernization. I argued that fusion-driven visual systems and digital awareness ecosystems may be advancing faster than the human brain can reliably use them in moments of extreme danger.
What followed was instructive. Several officials noted that they were already hearing similar concerns from elite special operations forces and combat aviators: These systems perform exceptionally well in deliberate, low-stress conditions, but become harder to use at the edge of consciousness, when life-threatening decisions must be made instantly.
The issue is not that the technology is poor. On the contrary, it is extraordinarily sophisticated. The problem is that it is increasingly misaligned with how the human brain functions under the stress of lethal environments.
This is not a marginal technical critique. It is a structural challenge emerging at the intersection of human physiology, combat psychology, and defense modernization. Unless the trajectory changes, Western militaries risk fielding systems that excel in demonstrations and controlled testing, yet underperform in close combat—not because they fail technically, but because they do not align with human biology when it matters most.
The tension between advancing technology and human limits points to a broader design challenge. This can be understood as a problem of augmented performance physiology. In this view, effectiveness depends not on adding capability, but on how systems interact with the human body and brain as our physiological state shifts under stress.
The Promise—and Pressure—of Fusion
Modern soldier visual systems are moving decisively toward fusion. Thermal sensing, low-light intensification, digital overlays, navigation cues, and networked information are increasingly combined into a single visual field. Under controlled conditions, these systems improve detection, expand awareness, and enhance understanding of the battlespace.
From a program perspective, fusion appears to represent inevitable progress; maximum information presented to operators at the tactical edge, in real time, should provide overmatch against an adversary. Yet operational feedback suggests a more complicated reality. As information density increases, the usability of these systems can degrade under stress rather than improve. As fusion architectures expand beyond individual devices into persistent, networked ecosystems supporting dismounted operations, the consequences of misalignment with human physiology grow more severe—not less.
The Friction Point: The Brain Under Threat
When a soldier encounters sudden danger, cognition does not remain calm or analytical. The body transitions instantly into survival mode through two tightly coupled biological systems. The sympathetic–adreno–medullary system triggers an immediate surge of adrenaline and noradrenaline, accelerating heart rate, narrowing focus, and biasing perception toward immediate threats. Shortly thereafter, the hypothalamic–pituitary–adrenal axis releases cortisol to sustain vigilance and energy availability. Together, these systems compress cognitive bandwidth, reduce working memory, narrow perception, and shift the brain away from interpretation toward rapid pattern recognition.
In this state, the brain prioritizes clarity over richness, simplicity over complexity, and speed over precision.
It wants clean edges, unambiguous motion cues, and the shortest possible path from perception to action. This physiological reality is where many fusion-based systems struggle.
A fused display may present thermal contours, intensified imagery, depth cues, symbols, route markers, and other overlays simultaneously. Technically, this is a remarkable achievement. Physiologically, at the moment of danger, it can be counterproductive.
Operators report that layered imagery becomes harder—not easier—to use under conditions of intense stress, simply because the brain’s stress response actively reduces its capacity to integrate complex visual information. The system functions as engineered. The soldier functions as biology dictates. The mismatch is the problem.
Imagine a mountain training exercise at dusk. A patrol advances toward a suspected observation point. At extended range, a fused imaging device performs flawlessly, revealing a faint thermal silhouette invisible to the naked eye.
As the patrol advances, the terrain and failing light compress engagement distances far faster than anticipated, turning a long-range observation problem into a close-range contact scenario. As the threat shifts from distant possibility to immediate contact, physiology takes over. Heart rate surges. Breathing shortens. Focus narrows. Vision tunnels. What had been a richly informative display minutes earlier now demands interpretation at the precise moment the brain has abandoned interpretation entirely.
A simpler analog image—single-spectrum, latency-free—would have required no cognitive reconciliation. It would have been processed faster, because it aligned with what the brain had become in that instant. In close combat, speed is clarity.
This is why many elite units retain traditional image-intensifier systems for close engagements. These devices deliver a continuous, unambiguous image that aligns with human neurobiology under stress. There is no perceptual dissonance, no layered truth to reconcile, and no cognitive friction. The analog system is not inferior. It is biologically coherent.
There is nothing inherently wrong with fusion technology. The problem lies in how it has evolved. In aviation, interface design advanced in lockstep with pilots. Cockpit layouts, symbology, and automation were shaped over decades by direct pilot experience, physiological research, and iterative feedback. The result was technology that adapted to human limits. Many modern soldier-worn visual systems followed a different path. They matured largely in laboratories, engineering programs, and demonstrations, only later being imposed on the human brain under combat stress.
In effect, the technology evolved first. The soldier is now being asked to adapt. There are sincere efforts underway to correct this through warfighter-centered design and adaptive interfaces. But unless those efforts begin with a realistic understanding of what the human brain becomes under intense stress—not in controlled testing, but in moments of existential threat—design intent risks being overtaken by biology. Aviation learned long ago that interface design begins with physiology. Ground combat systems have not yet fully absorbed that lesson.
Where Fusion Excels—and Where It Falters
Fusion is transformative for activities in which there is time not only for sensing, but also for processing: reconnaissance, surveillance, perimeter defense, mounted operations, and deliberate observation. When cognitive bandwidth is available, richer information improves understanding.
Fusion struggles when time collapses: during close combat, rapid movement, and unexpected contact. Unlike aviation interfaces used by highly selected and continuously trained aircrew, ground combat systems must perform across a wide range of ability, experience, and stress tolerance—including the median soldier operating under extreme environmental, cognitive, and physical load. This distinction appears consistently in operational feedback, even when it is underrepresented in program documentation.
The Cultural Bias Toward Digital Complexity
Another subtle influence shaping modern soldier interfaces is cultural rather than technical. Digital design paradigms—persistent overlays, dense symbology, constant augmentation—are increasingly familiar due to gaming and other virtual environments. These paradigms work well for users who are seated, safe, calm, and cognitively available.
Combat removes all of that.
The gaming interface model assumes attention is the limiting factor. Combat physiology makes survival the limiting factor. Importing this aesthetic into soldier systems risks designing for a mind that does not exist in a firefight.
Toward a Physiology-Aware Future
The central risk is not technological ambition, but engineering detached from biology. The next real advance will not come from adding more data to the display. It will come from presenting less—but more appropriate—data based on the operator’s physiological state. Future systems must interpret not only what the soldier sees, but what the soldier is becoming in that instant, dynamically simplifying the visual field without requiring conscious interpretation. Achieving this is extraordinarily difficult—but anything less will continue to collide with human limits. If the objective is to measurably improve combat effectiveness today, the most reliable gains may come not from additional layers of fusion, but from advanced situational-awareness training paired with lightweight, high-performance analog systems that align with human biology under stress.
Modern defense procurement increasingly absorbs the logic of the technology sector: Define a future, declare it inevitable, and build momentum until resistance becomes institutional risk. When belief attaches itself to capability narratives, it becomes harder to ask whether the human being who must fight with the system is actually better off.
There are few experiences that change a person’s beliefs faster than combat, where tools that fail to deliver are quickly abandoned in favor of whatever still works under pressure.
Technology will continue to advance rapidly. Human physiology will not. The question facing modern militaries is whether they choose to design around that reality—or relearn it the hard way.
Alan Kearney is a retired army commandant with thirty-seven years of service in the Defence Forces, Ireland. He has operational experience in Lebanon and Afghanistan, and specialist expertise in NATO-aligned explosive ordnance disposal, counter-IED, CBRNE defense, and counterterrorism training across Europe and the United States. He currently works in the international defense sector, leading research, capability development, and business engagement in night-vision technology, human performance, soldier survivability systems, and counter-UAS solutions.
The views expressed are those of the author and do not reflect the official position of the United States Military Academy, Department of the Army, or Department of Defense.