Tactical Display for Soldiers: Human Factors Considerations (1997)

The conditions under which military missions are or are likely to be conducted are increasingly varied with respect to the physical conditions, the number of tasks, and task complexity. Soldiers in today's Army are involved not only in war, but also in antiterrorist operations, catastrophe relief, and peacekeeping. Each of these missions could require different equipment configurations to achieve optimal soldier performance. And each entails sources of environmental stress that have implications for the soldier's equipment. This chapter provides a basis for our discussion of the human factors considerations related to the Land Warrior System and the subsystems that constitute the helmet-mounted display, describing the military environment in which the proposed new system and subsystems are expected to be used.

The abilities of the soldiers and the unit to shoot, move, communicate, and survive are the important measures of combat performance for military units, including infantry squads and platoons. Advanced weapons systems and new technologies offer the possibility of increasing individual and unit performance. Advanced weapons technology linked with rapidly unfolding information technology holds the promise of increased speed, accuracy, and lethality for the Land Warrior of what the Army calls "Force XXI" (U.S. Department of the Army, 1994). These technological advances could make soldiers and their units significantly more effective than they are today. However, realizing this potential can

be achieved only if the new technology reduces a soldier's fear of going into combat, diminishes the uncertainty of success in combat, and makes it physically less demanding for soldiers and their units to achieve mission success. The land warrior of tomorrow, equipped with sophisticated system capabilities, will be a more formidable fighter only if the new systems build individual soldier confidence and enhance unit cohesion.

The mission of the infantry soldier in a war-fighting environment in the 21^st century will not be dramatically different from the mission of today's soldier. In a war-fighting sense, tomorrow's land warrior will still be required ''to close with and destroy the enemy by means of fire and maneuver to defeat or capture him, or to repel his assault by fire, close combat, and counterattack" (U.S. Department of the Army, 1992). However, the role of tomorrow's land warrior may well be changed in significant ways. In recent years, infantry soldiers have been committed to a series of less than combat employments in Somalia and Haiti. The infantry soldiers of tomorrow could be required to react to an even broader array of noncombat or not-active combat requirements, such as peace enforcement, stabilization and civil support missions, counterinsurgency and counter terrorism, humanitarian relief in a potentially hostile environment, and political interventions. Changing international power balances may increase the frequency of low-intensity conflicts, bring about increased counter terrorism actions, and expand the range of peacekeeping tasks.

In these settings, rapidly changing danger situations, avoidance of civilian casualties, restrictive but variable rules of engagement, and the wide dispersal of small units place increased demands on effective communications, accurate position reporting, and detailed intelligence gathering. In general, such roles place soldiers and small units in an environment in which the enemy threat is often unclear, unit dispersions are potentially much greater, and the appropriate response and battle actions are more uncertain. Such changes add to the task of battle-hardening soldiers and their units to deal with the uncertainty and fear of combat.

Since the end of World War II, the infantry, like the entire Army, has been prepared to respond to a broad range of combat and combat environments. Infantry soldiers have been trained to meet the challenge of high-intensity nuclear war in Europe; to mid-intensity conflict in Europe, the Middle East, and Korea; and low-intensity conflict in Third World countries around the world. For the past 40 years, the Army has been guided by the presence of a clear threat, which led to

prescribed doctrine and to weapon systems and organizations driven by capabilities of the threat.

With the end of the cold war have come fundamental changes in the nature of the threats to U.S. security and to the approach of doctrine and organizations. As a result of threat changes, advances in technology, new weapons, and digital information systems, the infantry soldier of the future may see significant changes in basic unit organization at the squad, platoon, and higher levels. The requirement for new, flexible Army doctrine has been clearly presented (see U.S. Department of the Army, Training and Command Center, 1994). This first look into the future characterizes the new battle dynamics of the Force XXI with new dimensions in battle command, battle space, depth and simultaneous attack, and early entry. These dynamics project decreases in the number of soldiers committed to a mission, decreases in mission duration, increases in individual and unit dispersion, extended engagement ranges, increased speed of maneuver, and more complex combat maneuvers. Increased distances and faster tempos add emphasis to the need to prepare individual soldiers and small units to overcome the fear and uncertainty caused by isolation and rapidly occurring battlefield events.

In the past, the cohesion and fighting confidence within a squad or platoon could be maintained by the close proximity of the unit members, by direct and personal leader contact, by local visual contact, and by the direct reinforcement of hand and voice signals. In critical close combat situations, individual performance and unit confidence were enhanced by drawing even closer together or by more deliberate and controlled movements. The use of tomorrow's Land Warrior will tax a unit's ability to retain its confidence and cohesion in the face of greater individual dispersion and the potentially increased speed of maneuver required just to survive on a more lethal and potentially less defined battlefield.

All of the expected differences in the nature of the battlefield reinforce the requirements for increased soldier performance and for appropriate use of new technologies. These requirements include accurate and almost instantaneous information about the position of friendly and enemy elements; more effective communications, down to and within the infantry squad; more accurate and longer-range day and night engagement systems; and increased soldier protection.

These changes and improvements must be achieved by balancing the sensibilities and capabilities of individual soldiers and small units with the advantages and capabilities of new technologies. The changes must address the issues that new technologies raise with their potential for separating a soldier from his local physical environment and the more direct personal contact of today's battlefield.

The use of enhanced technology must also be achieved without placing unmanageable cognitive demands on soldiers that could shorten the duration of time allowed for individual performance, that could retard individual response time, or that could become physically debilitating under combat conditions.

Other challenges also affect the nature of combat for tomorrow's infantry.

The end of forward stationing of U.S forces on overseas bases adds greater importance to the issues of deployability and sustainability. Lower budgets reduce the level of infantry forces; they also reduce training dollars and increase the importance of enhancing soldier effectiveness. These same constraints add emphasis to requirements for joint and combined operations and the need to have U.S. infantry soldiers trained, equipped, and able to interface flexibly with a wide range of organizations and systems. These requirements add to the number of tasks for which soldiers must train to maintain their level of combat readiness; they add, as well, to the range of environmental conditions under which the varied missions may have to be conducted.

In addition to these challenges, future employments and the technical complexity of future weapon systems will increase the number of training tasks required and decrease the time available for training. It is likely that a greater number of future infantry soldiers will be part of the National Guard or Army Reserve force structure. This sharply reduces the time they are available for training, since Guard and Reserve soldiers have significantly less time available to train and maintain readiness. These conditions add new dimensions to the problems of maintaining individual and small unit combat readiness. They add as well to the difficulties of developing physical and psychological readiness.

The Land Warrior System is a major research and development effort by the U.S. Army to equip infantry soldiers for the high-technology battlefield of the future. In addition to improving lethality, command and control, survivability, mobility, and sustainability for individual infantry soldiers, it is being designed to provide vision enhancement (under both daytime and nighttime conditions), secure voice communication, greater protection, reduced load, and adequate support for individual maintenance in the tactical environment. Military planners have conceptualized an ensemble of equipment that includes new protective garments, armaments, and information-processing elements. The visual display component of the information-processing subsystem is envisioned as a flip-down monocular presentation device mounted to one side of the soldier's helmet.

The complex technology and pervasive impact of the proposed Land Warrior System on infantry soldiers raise a number of basic doctrine questions about the autonomy of an individual soldier. Is it a design objective to give tomorrow's land warriors information that could allow them to make more independent decisions about their individual tactical actions? At the level of system design, this issue translates into questions about control prerogatives. For example, should an individual soldier decide when a display will be used or moved out of view? If so, should an individual soldier be able to choose the kind of information being presented? Also, should soldiers be able to call up the latest map overlay whenever they want to see it? The concept of a helmet-mounted display with a flexible

set of modes or displays that allow soldiers to view different levels of information presentations has significant potential for cognitive distraction. (The negative and positive effects that multimodal displays can have on immediate individual situation awareness are addressed below.)

Other questions concern the nature of two-way communications in the chain of command. Information acquired by an individual soldier from advanced sensor systems (image intensifier, infrared, video camera, lasers, etc.) is intended for use at battalion and higher levels. Should such information be transmitted directly to higher levels or through each level of the chain of command? Is there an operational trade-off between delays in transmission and the possibility of misunderstanding the message at higher levels or misunderstanding the operational situation if intermediate levels do not process the information? Historically, in demanding combat situations, low level leaders could and would reduce the flow of higher-level instructions and orders by ignoring or not answering transmissions. Will the Land Warrior communications system cause even greater potential for selective avoidance of communications? How will communications security be addressed? What happens if components of the system fall into enemy hands? How will intelligence updates be processed down to the soldier level? Will the squad leader organize and filter information for uploading? Other questions concern the amount or level of interaction among squad members to correct or update visual data and set priorities for information. Although procedures can be developed to address these questions, the most significant question is whether the Land Warrior System will create a situation of task and information overload for individual soldiers and lower-level leaders. The issue is information management. Is there to be a team-based approach to information management and, if so, how is the information distributed among squad members?

The essential measures of human performance for tomorrow's land warrior are not different from those of today's infantry soldier-speed and accuracy. The time it takes a soldier to execute, with precision, a critical combat task is the measure of battlefield success and survival. In combat situations, survival depends on soldiers' ability to rapidly detect, identify, and successfully engage a hostile enemy before the enemy can successfully engage them or their units. Detection and identification rely on the ability to perceive obstacles in the environment, the layout of the terrain, and the location of the present site within the more general situation. For small unit combat actions, this infantry capability is supported by at least three other essential capabilities: accuracy by unit leaders in knowing and reporting their unit's location; the accuracy and timeliness with which unit leaders know the location of friendly units and elements within the range of the weapon systems they control; and the ability to report enemy locations accurately, rapidly, and stealthily.

The infantry rifle platoons and squads of today, and probably of those tomorrow as well, must be prepared to conduct three basic tactical operations: movement, offense, and defense (U.S. Department of the Army, 1992). All of

these operations are conducted by day and night, in conditions from desert heat to winter snows, and in terrain that varies from flatlands to swamps to mountains.

Under wartime conditions, all infantry missions are planned for execution on a 24-hour-a-day basis. This places great stress on the need for endurance and physical conditioning.

Battle success requires the successful execution of a series of critical individual, collective, and leader tasks. Many of these critical infantry tasks overlap and recur many times across all squad and platoon missions. Table 1-1 highlights the critical Land Warrior battle tasks for an infantry soldier, squad leader, and platoon leader for three of the most significant infantry missions: reconnaissance, attack, and defend. The relative importance of specific tasks will vary, depending on the conduct of a particular mission and the level of intensity of combat. For example, the time available for planning varies with the timing of a mission and whether the conflict is a mid- to high-intensity operation, a low-intensity operation, or an operation other than war. In planning for a move in a mid-intensity environment, there may be days available, but in a hasty attack in the same environment, there may be only minutes. In an operation other than war, a squad leader with a mission to defend a key area and control elements of the civilian population would be very focused on the rules of engagement, identification of potential threats, and ensuring appropriate use of force; in contrast, in a mid-intensity defend mission, the leader would be concerned with planning fires, controlling direct fires, and rapid response with all and any firepower available. These tasks and those for the squad leader are drawn from the Hardman III Analysis of the Land Warrior System (Adkins et al., 1995).

To understand the human factors effects of the proposed Land Warrior System with its helmet-mounted displays, it is necessary to correlate the critical tasks that infantry soldiers and leaders must accomplish and the functional capabilities of the proposed system. Tables 1-2, 1-3, and 1-4 are a series of matrices of Land Warrior System components associated with their expected battlefield enhancements (lethality, tempo, survivability, and mobility) and with key battle tasks performed within a rifle platoon by infantry soldiers, squad leaders, and platoon leader, respectively. The tables do not indicate whether the component aids a soldier or leader in accomplishing a task but only whether the component potentially affects the task.

Although the tasks of the land warrior and his unit may appear relatively simple in terms of these tables, they are in fact difficult because of the need for precise execution by a soldier (with varying cognitive, physical, and general skill

levels) and for rapid coordinated execution by the entire unit under battlefield conditions. For example, during a unit attack, when contact with the enemy is made, accurate and responsive reporting of all information is essential in order to rapidly generate combat power at the point of contact and the appropriate element of enemy's combat power.

The first few seconds after enemy contact determines the fate of the maneuvering fire team. On enemy contact, soldiers might immediately drop to the ground, roll for cover, and return rapid fire in an attempt to suppress the enemy fire, or they may be required to rapidly move out of the kill zone and seek cover. In an instant, soldiers wearing a helmet-mounted display would have to execute a broad range of cognitive processing and physical activity: detect and analyze the threat, its location, and effect; drop and roll and return fire or run at a sprint; or drop to cover and call for fires on the enemy position and, perhaps, return direct fire on the location. If at that moment the Land Warrior System display interferes with the soldiers' immediate situational awareness or hinders their physical movements, all the system's technological capabilities may not matter.

The first minutes after an initial enemy contact determine whether the squad and platoon will be successful in maintaining contact by rapidly increasing rates of fire and executing squad maneuvers to fix the enemy. Knowing friendly positions and the location of the enemy accurately is essential if requests for fire support are to be timely and effective. In the future, because of the potential for increased dispersion and more rapid movement, it will be more imperative and time-sensitive for those in higher-level command and control positions to know the exact location of all friendly forces in order to provide responsive coordinated support and at the same time avoid casualties from friendly fire.

During the conduct of an attack, the physical and neurological responses of a soldier could be critical to his survival. Today's soldiers already have an almost overburdening load of equipment. If the added weight of Land Warrior System components slow them or distract their attention from the local surround, even unintentionally, the outcome could be negative.

The design of the helmet-mounted display must be compatible with the physical responses a soldier has to make and, to be effective, must accommodate the different psychological and neurological capabilities of different soldiers. A flexible display with a selection of modes of information presentation and levels of detail may not be fully compatible with the capabilities of a given soldier or with the actions required in battle. An illustration of a negative impact is the disorientation that an individual soldier would experience if he were moving at night, wearing a helmet-mounted display in a night vision mode with a field of vision of 60 degrees, when suddenly his unit is engaged. He drops to the ground and rolls to cover, switches to the night thermal sight with a field of vision of 9 to 15 degrees, and attempts to determine the direction of enemy fire of which he is totally unsure. At the same time, the impact of a bright flare shuts down his night

vision devices, and the soldier may be disoriented to the point of not being able to make a response.

At the squad level in an attack, the situation may be different. The critical tasks that the helmet-mounted display supports include controlling direct fires, maneuver, and coordinating indirect fire support. A successful squad attack requires a squad leader to rapidly adjust the direct fires of his unit; accurately report the situation, including the location of his unit; make timely calls of fire support; and control the maneuver of his squad. All of these actions must occur under enemy fire and amidst confusion and uncertainty.

Defensive operations may have a different set of effects on the design of the Land Warrior System. A defense can be characterized by periods of intense preparation, followed by irregular periods of boredom and observation waiting for enemy activity, and then the overwhelming impact of an enemy closing in on the defensive position. Preparation for defense is an intense, day-night, physically demanding, individual, and team effort. After intense preparation, leaders and soldiers are often physically and psychologically stretched. The impact of the helmet-mounted display could be a stress multiplier if its design causes a false sense of capability or a lack of local situation awareness that leads to ineffective soldier responses.

In defensive operations, leaders fight by ranging targets, setting priorities for targets-what and when to fire-controlling fires to destroy the nearest or most dangerous, and shifting direct, indirect, and indirect supporting fires. These actions require constant communications and rapid information flow with accurate reports when soldiers and leaders may not be at peak physical and psychological levels. The design of the Land Warrior System and the helmet-mounted display have to meet these challenges to achieve their expected potential. Using a helmet-mounted display that has a selection of modes effectively means that the leaders and soldiers must have a way of determining what information is needed, so that everyone has the correct situation awareness at the same critical time. In defensive operations, the system must allow for the individual capabilities and differences of the soldiers using it.

Although any given task may not be particularly demanding in a benign environment, the collective squad or platoon tasks associated with shooting, moving, and communicating are performed under conditions of great stress. The sources of stress include the nature of the mission, resource availability, perceived risk, information uncertainty, physical demands, fatigue, time, environmental conditions associated with weather and terrain, and surprise. As a result of these stresses, a soldier's state of arousal varies from prolonged boredom to short periods of stark terror. Much of the cognitive workload is the resuzlt not only of the tasks to be performed, but also of the standards to be achieved and the

conditions under which the tasks have to be performed. The challenge for system design is to avoid unanticipated negative consequences that will impair confidence, cohesion, commitment, and communication. Losing or degrading the quality of information a soldier is currently receiving under daylight conditions and which he perceives to be critical could affect how and under what conditions he will use the system.

Success in combat requires that infantry soldiers control their fear and behave in a predictable manner, no matter how tired they are or how uncertain the situation is. In order to elicit this behavior, commanders attempt to build high performing, cohesive, and confident units by clearly defining roles and jobs, keeping soldiers informed, conducting realistic and demanding individual and group training, and providing strong leadership and competent supervision. The introduction of new technologies and capabilities adds, deletes, or modifies tasks; affects how tasks are performed; changes job requirements; enhances or degrades confidence and cohesion; changes training requirements; and affects the acquisition and retention of personnel. The Land Warrior System is not an exception: it will affect how leaders define soldiers' roles and jobs and how they communicate with and train and lead their units.

Military commanders have known for centuries that fear is easier to cope with in groups than in isolation. Building confidence at the individual and unit levels is essential to overcoming fear. As a result, ''buddy" systems have existed for many years. Extending the buddy system concept through the fire team, squad, platoon, and company levels builds unit cohesion and instills trust and interdependence in a larger group. Technology can facilitate or hinder unit cohesion, depending on how it is designed and used. Communication technology allows soldiers to feel a part of a unit despite geographical separation. In contrast, a display that reduces vision in daylight, induces motion sickness, increases workload and reading time, causes discomfort, or requires constant adjustment will negatively affect individual confidence and unit cohesion.

Individual and collective training is conducted to improve confidence, overcome fear, and enhance performance reliability. With sufficient training, soldiers know that they can execute assigned tasks under all conditions and achieve or exceed the expected standards. Training helps the soldiers gain confidence in their roles within the unit for any specified mission. The military structure assists in establishing, maintaining, and reinforcing clearly defined roles. Role clarity fosters interdependence and trust as well as confidence. The reporting procedures associated with new technologies could undermine this structure and erode soldier confidence in unit leaders if they are used to bypass the structure.

Radios have been used reliably at the platoon level and higher and for many years. Although platoon and squad radios have existed, they have not always been reliable, and squad members do not carry radios. As a result, communication below the platoon level has historically relied on visual or auditory contact with another member of the unit. But hedgerows, dense jungles, mountainous

terrain, and urban environments make it difficult to maintain visual and auditory contact. The effects of poor communication on maintaining a cohesive fighting force, avoiding fratricide, and shortening battle execution time are obvious.

Communications in the military usually include orders and instructions flowing from the headquarters to soldiers, and information about the battle situation flowing from small unit leaders to the headquarters. As communication technology has improved, so has the demand for information at the headquarters level.

When these demands from headquarters are not synchronized with the work ongoing in units that are engaged in battle, the communication process itself can reduce battle effectiveness by diverting leader attention and by adding stress to an already overstressed situation. Personnel who are overworked will shed tasks until they achieve a level they can manage. Reporting takes time and can be a major workload factor; technology should be used to reduce this workload, not to increase it.

The natural human tendency is to want more information, not less. Each information requirement should be questioned as to who needs it, when they need it, under what conditions they need it, and how they will use it. In terms of display, more information frequently leads to more complex screen designs, navigation menus, function keys, and other control mechanisms. Ultimately this could further contribute to reduced situation awareness, with the unintended consequence of decreased survivability.

In 1959 General Bruce C. Clarke stated: "The truth is that the most expensive weapon that technology can produce is worth not an iota more than the skill and will of the man who uses it." The challenge for engineering design is to use technology to improve a soldier's skill and will. History is replete with examples of technological advances that were introduced into the military before they were introduced into society in general and did not have the desired effect (Guilmartin and Jacobowitz, 1984).

The use of new technologies to improve communication, provide rapid access to data on enemy and friendly positions, improve soldier protection, and provide more accurate daytime and nighttime engagement systems implies improved combat effectiveness. Command and control at the battalion task force and higher levels should improve; it is not evident, however, that the use of new technology will help the squad leader during wartime operations as much as it does higher echelons of command. Although command and control is clearly outside the scope of this study, we believe that an important consideration in evaluating the helmet-mounted display design is how well it helps or hinders the squad leader and the platoon leader in doing their jobs. To that end, it is important to understand decision making at the squad level and its impact on workload and squad performance.

Decision making consists of choosing between alternative courses of action (Buck and Kantrowitz, 1983). The quality of a decision is heavily dependent on the information available to the decision maker. Consequently, the processes of communication cannot be separated from the processes of decision making. The first step in any decision making process is the recognition that some action must be taken. In scientific terms, the decision maker observes that a salient condition is not within some bounds of tolerance. This could be as simple as the recognition of hunger, with the prime decision being that of taking action to seek food.

In a combat setting, the typical instance might be the detection of an immediate threat for which the action could be to take cover or attack. However, in both instances, the initial observation plus action selection is only the preliminary stage to what can become a long series of incremental decisions. In the combat situation, the sequence would include a determination of optional means to counter the threat, calculations of the risk factor and the likely outcome from each such means, and selection of a course of action intended to suppress or eliminate the threat.

It is clear that, in combat, leaders are confronted with anything but trivial decisions. They are deeply engaged in information collection and absorption, the formulation of mental representations of external conditions (situation awareness), the assessment of probabilities, and the weighing of the options to give a net outcome value. In this regard, the complexity of the problem can easily exceed the mental capacities of the decision maker and lead, in turn, to the need for provision of external support, such as decision aids of one kind or another.

Over the years the Army has evolved a number of techniques for managing the workload and communication at the squad level. Generally these have involved the use of standard operating procedures, battle planning, rehearsals, battle drills, crew drills, and extensive training under realistic conditions. The result has been to reduce the need for communication and increase the speed of battle execution. Essentially the squad leader and the squad learned to quickly identify a situation and react to it with a battle drill rather than have to think about it. The role of the squad leader was to lead by example. He was not required to creatively solve new problems without assistance from his platoon leader or platoon sergeant.

The helmet-mounted display has the potential for significantly increasing the workload of the squad leader by adding both information-gathering and decision making tasks to his existing job. Some squad leaders read and write at a minimally acceptable level, mastering other techniques for learning. The helmet-mounted display will require the squad leader to read and write more than he has historically. Under these conditions, it is anticipated that the squad leader will be slow and deliberate and will gain in speed only with training; as a result, his initial workload levels will be very high. When these new tasks are combined with the time stress associated with battle, many squad leaders will be overloaded.

Other concerns are raised by the fact that the helmet-mounted display will separate the squad leader from his natural view of the environment. The extent of this separation is not known, nor is the impact of it fully understood in terms of performance. Viewing the world through the display at night, rather than reading the display to extract or enter data, removes the squad leader from the environment in different ways.

It may be that the helmet-mounted display will be of greatest assistance to the squad leader in operations other than war. Such operations pose a unique set of challenges, which require exercising a different degree of control over the use of military force than conventional wartime operations, with relatively clear rules of engagement. Whether or not the technology will improve battlefield effectiveness will be determined in part by the quality and timeliness of the decisions made by the squad leader and the chain of command.

There are a number of important questions that should be addressed by the Army regarding the implications of the helmet-mounted display for information processing and decision making:

• How do decision making factors vary in order and significance from situation to situation, and what does that mean for the design of the helmet-mounted display?
• To what extent does local situation awareness¹ affect decision making at the squad level?
• To what extent does global situation awareness² affect decision making at the squad level?
• How should presentation formats be designed for decision making under stress (defined as decisions that have to be made in less than a minute with incomplete information)?
• To what extent do poor resolution, field of view, and depth perception affect decision making?
• How will decision making aids be designed to support the squad leader?
• What decision making training is currently provided?
• To what extent does leadership contribute to good decision making?

The operating environment of today's infantry soldier is varied, complex, and demanding. The environment of tomorrow's land warrior may well be even more varied, more complex, and more demanding. The design issues for the

helmet-mounted display of Land Warrior System that are raised by this discussion of the future infantry battlefield can be summarized in four key themes.

First, what critical doctrinal and employment priorities must or should the Land Warrior System and the head-mounted display meet? Force XXI projections identify changes in the scope of future infantry tasks and present a view of an expanded range of future infantry missions. These projections for tomorrow's land warrior highlight the need for a more clearly defined Land Warrior System doctrine. For example, is the design objective to give tomorrow's land warriors information that could allow them to make more independent decisions about their individual tactical actions? An integrated battlefield information and weapon system incorporating the latest electronic technology cannot be effectively achieved without clear employment concepts. Developing the design of the helmet-mounted display requires technical trade-offs, not only in achievable technology but also in human performance. No one set of trade-offs will optimize human performance under all conditions. The most advanced technical capabilities will not improve human performance unless the system is reliable and builds confidence.

Second, what are the limitations of the cognitive, psychological, and physical capabilities of the infantry soldiers in the active force, the National Guard, and the Army Reserve who will use the Land Warrior System? In order to achieve the expected enhancements in human performance, the Land Warrior System and its head-mounted display must be designed to support the mental, psychological, and physical characteristics of tomorrow's land warrior. Complex electronic displays and battle sights will not achieve the Army's goal if they provide overwhelming levels of information that a soldier may not need and may not be able to process effectively under critical battlefield conditions.

Physical ergonomics also plays a critical role in achieving the success of Force XXI Land Warrior. There could be no more disastrous scenario for advanced battlefield technology than the prospect of squads of soldiers so engrossed in making the equipment work that they become easy targets for the enemy. In contrast, a well-designed, effective information system could not only improve efficiency but also could mitigate effects of stress, which have been a traditional barrier to mission effectiveness in conflict situations. It is important to understand the mechanisms of stress and how they interact with the proposed technology. How to suppress the vibration in a head-mounted display that is caused by walking is also a question for research and design.

Third, what are the significant implications of the Land Warrior System for testing and evaluation? The desire to rapidly develop and achieve a Land Warrior System that applies significant technological advantages to the infantry battlefield requires the development of a comprehensive and thoughtful test and evaluation strategy. The rapid advances made in computer and electronic systems can sometimes lead to expectations about capabilities that are not achievable, do not work, and are not supportable under any realistic battlefield or employment con-

ditions. The Land Warrior System and head-mounted display must be systematically tested in a range of realistic battle conditions, not only to aid the development and refinement of employment doctrine, but also to validate technical capabilities, system performance, and development priorities. Given the lack of information about human performance with helmet-mounted displays in which the body is in motion, a comprehensive test program is needed that considers helmet stability, helmet display capabilities, perceptual understanding and comprehension, and variance associated with individual differences.

Fourth, what are the critical issues in selection, retention, and training of future infantry soldiers'? The area of training requires focused attention. The design of the Land Warrior System and its head-mounted display not only must be logistically supportable in terms of reliability, availability, and maintainability, but must also result in a system that soldiers can be taught to use effectively, efficiently, and confidently. If the complexities of the display and the system require extraordinary personnel selection or training demands that do not allow the development and maintenance of combat proficiency in infantry soldiers, then their combat potential could be lost.