A military exercise or war game is the employment of military resources in training for military operations, either exploring the effects of warfare or testing strategies without actual combat. This also serves the purpose of ensuring the combat readiness of garrisoned or deployable forces prior to deployment from a home base.
War games involving two or more countries allows for better coordination between militaries, observation of enemy's tactics, and is a visible show of strength for the participating countries.
Exercises in the 20th and 21st centuries have often been identified by a unique codename, such as Cobra Gold, in the same manner as military contingency operations and combat operations like Operation Phantom Fury.
Soldiers from Britain's Royal Artillery train in a virtual world, 2015
Military exercise in Ystad
, Sweden, 2015
Command Post Exercise
- A Command Post Exercise (CPX) typically focuses on the battle readiness of staffs such as a particular Unified Combatant Command or one of its components at any level. It may run in parallel with an FTX or its equivalent, or as a stand-alone event for headquarters staff only with heavy emphasis on simulated events.
- Historical names for the field exercise, or the full-scale rehearsal of military maneuvers as practice for warfare in the military services of the British Commonwealth include "schemes," while those of the military services United States are known as Field Training Exercises (FTX), or, in the case of naval forces, Fleet Exercises (FLEETEX).
- In a field exercise or fleet exercise, the two sides in the simulated battle are typically called "red" (simulating the enemy forces) and "blue", to avoid naming a particular adversary. This naming convention originates with the inventors of the table-top war-game (the "Kriegsspiel"), the Prussians von Reiswitz; their army wore Prussian blue, so friendly forces were depicted by the color blue.
- Several different armed forces of the same nation training together are described as having a joint exercise, while those involving forces of multiple nations are described as having a combined exercise.
- These latter events incorporating multiple nations have often been referred to as NATO exercises, Coalition exercises, Bilateral exercises (based on security arrangements/agreements solely between two nations), Multilateral exercises (based on security arrangements/agreements between multiple nations), or other similarly named events.
- Other types of exercise include the TEWT (Tactical Exercise Without Troops), also known as a sand table, map or cloth model exercise. This type of exercise (in recent years assisted by computer simulation) allows commanders to manipulate models through possible scenarios in military planning. This is also called warfare simulation, or in some instances a virtual battlefield and in the past has been described as "wargames." Such examples of modern military wargames include DARWARS, a serious game developed since 2003 by the US DARPA agency with BBN Technologies, a defense contractor which was involved in the development of packet switching, used for ARPANET, and which developed the first computer modem in 1963.
- A subset of simulated exercises is the Table Top Exercise (TTX), typically limited to senior personnel stepping through the decision-making processes they would employ in a crisis, a contingency, or general warfare.
NATO exercise codenamed A Certain Sentinel, in Nuremberg, Germany January 1986.
German pre-war military exercise Herbstmanöver
in southern Germany autumn 1909 (Emperor Wilhelm II
second on the left)
US Army Europe
soldiers on winter maneuvers in Germany during Operation Warsteed 87, in 1987.
The modern use of military exercises grew out of the military need to study warfare and to 'reenact' old battles for learning purposes. During the age of Kabinettskriege (Cabinet wars), Frederick the Great, King of Prussia from 1740 to 1786, "put together his armies as a well-oiled clockwork mechanism whose components were robot-like warriors. No individual initiative was allowed to Frederick's soldiers; their only role was to cooperate in the creation of walls of projectiles through synchronized firepower." 
This was in the pursuit of a more effective army, and such practices made it easier to look at war from a top-down perspective. Disciplined troops should respond predictably, allowing study to be confined to maneuvers and command.
soldiers during exercise Joint Resolve 26 in Bosnia.
The stunning Prussian victory over the Second French Empire in the Franco-Prussian War (1870-71) is sometimes partly credited to the training of Prussian officers with the game Kriegspiel, which was invented around 1811 and gained popularity with many officers in the Prussian army. These first wargames were played with dice which represented "friction", or the intrusion of less than ideal circumstances during a real war (including morale, meteorology, the fog of war, etc.).
21st century militaries still use wargames to simulate future wars and model their reaction. According to Manuel de Landa, after World War II the Command, Control and Communications (C3) was transferred from the military staff to the RAND Corporation, the first think tank.
Von Neumann was employed by the RAND Corporation, and his game theory was used in wargames to model nuclear dissuasion during the Cold War. Thus, the US nuclear strategy was defined using wargames, "SAM" representing the US and "IVAN" the Soviet Union.
Early game theory included only zero-sum games, which means that when one player won, the other automatically lost. The Prisoner's dilemma, which models the situation of two prisoners in which each one is given the choice to betray or not the other, gave three alternatives to the game:
- Neither prisoners betrays the other, and both are given short-term sentences
- One prisoner betrays the other, and is freed, while the other gets a long sentence
- Both prisoners betray each other, and both are given mid-sized sentences
This modelization gave the basis for the massive retaliation nuclear doctrine. The zero-sum fallacy and cooperative games would be theorized only later, while the evolution of nuclear technology and missiles made the massive retaliation nuclear strategy obsolete.