adversaries. This book will discuss the current practitioner use of both wargames that investigate the human decision‐making processes and computer simulations that investigate the quantifiable aspects of combat. Our goal is to provide the reader a better understanding of how each tool brings unique qualities and attributes to bear on the assessment of the phenomenology of combat that allows our senior leaders to make better informed decisions.
Terminology
There are many different types of combat simulations that exist today, and in order to have a fruitful discussion we will need to adopt a standard lexicon. The first step in developing this lexicon is to define the terms “model,” “simulation,” and “wargaming.” A model is “a physical, mathematical, or otherwise logical representation of a system, entity, phenomenon, or process.”1 A simulation is “a method for implementing a model over time.”2 A wargame is “a representation of conflict or competition in which people make decisions and respond to the consequences of those decisions.”3 Often in today’s Department of Defense (DoD), the term “simulation” implies that all the models that comprise the simulation are instantiated in executable computer code, and because of that, most wargames are not thought of or referred to as “simulations.” From this point forward, when we use the term “simulation” it will refer exclusively to computer‐hosted closed‐loop combat simulations, and thus will not include wargames.
Combat simulations are categorized by the amount of human interaction required, the use of probabilistic processes and the level of war they represent. Combat simulations that require periodic human decisions are called “Human‐in‐the‐Loop” or H‐I‐T‐L simulations, and these are often used as computer‐hosted wargames, with human commanders or command and staff teams making the necessary decisions. Closed‐loop simulations have totally automated the human decision‐making processes in computer code and can simulate hours, days, weeks, or months of combat without any human intervention during the simulation’s execution. Simulations that will produce the same output for a fixed set of input parameters are deterministic, while simulations that have one or more probabilistic parameters whose value will be determined during the simulation’s execution using a random number seed are stochastic, which are sometimes referred to as “Monte Carlo” simulations. Simulations are also segregated by the level of war that they represent. A strategic simulation will represent an entire campaign, such as the European or Pacific theaters of war during World War II. An operational simulation will represent a specific operation that is part of a campaign, and a tactical simulation will represent some portion of an operation. In most cases, the higher the level of war, the more abstract the models of the simulation are. Most tactical simulations represent each weapon system and soldier of a unit and are called entity simulations. Many strategic simulations represent entire units, such as a company, battalion, or brigade, by aggregating the weapons systems and soldiers of a unit, and treating the unit as a single object with attributes derived by combining the attributes of the unit’s entities into a single value that represents some combat capability of the unit. In ground combat simulations, the single value assigned to such a unit is often called the “combat power” of the unit. These simulations are predictably called aggregate simulations.
Wargames are categorized by the purpose of the wargame, the manner in which players are engaged and the amount of information provided to players. There are three widely recognized purposes for defense wargames: analytic, educational, and experiential. Educational and experiential wargames seek to impart knowledge or experience, respectively, to its players. In other words, these wargames produce better educated or more experienced players. Analytic wargames are designed to address an objective and a set of issues that the wargame’s sponsor provides. The products of an analytic wargame are findings that address the sponsor’s objective and issues. Wargames are also categorized by the method that the players interact. Players are engaged directly in a seminar wargame and the facilitator of the wargame usually adjudicates any player interactions. Conversely, players engage each other indirectly in system wargames. In system wargames, there are usually models that are designed to adjudicate player interactions. Finally, wargames must provide players with information that they will then use to make their next decision. A wargame that only provides the players the information that would actually be available to them is called a closed wargame. In closed wargames, each side (typically red or blue) is sequestered in its own cell, and the wargame’s white cell makes the determination of what information each side’s collection assets would produce, and then communicates only that information to the appropriate cell. Wargames that allow all the players to have all available information are called open wargames.
And, as for the model or models that are used in simulations and wargames, users must heed the statistician George Box’s warning: “All models are wrong, some are useful.”4
An Abbreviated History of Wargames and Simulations
Before the rise of the computer, the primary form of combat simulation was wargaming. Wargaming has a rich history and has been used by many cultures and in many different forms. The ancient games of chess and Go are but a few of the games that were believed to have usefulness in training and testing military commanders’ decision‐making capabilities, and this belief led to the designing of games focused on modeling combat for the development of military leaders. In the nineteenth century, the Prussians developed Free and Rigid Kriegspiel as methods to educate their officers. Rigid Kriegspiel focused on the calculations of combat, with the hypothesis that good combat leaders had to be able to employ a type of “combat calculus” to mathematically understand what decisions should be made on the battlefield.5 Free Kriegspiel used battle‐tested Prussian officers to assess junior officers’ responses as they were presented with possible combat situations to which they had to react.6
In the early part of the twentieth century, F.W. Lanchester proposed two sets of differential equations that could be used to simulate combat, referred to as Lanchester’s linear and square laws. Although he proposed these laws to simulate aerial combat, they gained traction for use in modeling ground combat. The square law rewards a combatant’s ability to concentrate forces and was seen as relevant to modern warfare, and the linear law has been accepted as a model of ancient warfare where combatants were unable to mass fires.7 Lanchester came to realize, through studying the Battle of Trafalgar, that if a battle can be decomposed into a series of concurrent and consecutive sub‐battles, separated by space and time, then it is more appropriate to apply the square law to each sub‐battle, and sum all sub‐battle losses to gain a more accurate accounting of the entire battle than it is to apply the square law a single time to the entire battle.8 As computer‐based combat simulations were developed in the latter half of the century, many ground aggregate simulations used some adaptation of Lanchester’s laws to model attrition.9
In the first half of the twentieth century, the US Navy made great use of wargaming to examine a potential war with Japan, beginning over two decades of focused wargaming in 1919 at the US Naval War College.10 This detailed examination of war in the Pacific proved to be so successful that, after the conclusion of World War II, Admiral Chester Nimitz said “…nothing that happened during the war was a surprise – absolutely nothing except the Kamikaze…”
