War is a prolonged state of violent, large-scale conflict involving two or more groups of people. When and how war originated in humans is a highly controversial topic. Some believe it began only about five millennia ago, with the rise of the first states; afterwards war "spread to peaceful hunter-gatherers and agriculists" (Otterbein 2004: 31-32). Others (Azar Gat 2006 36-37) argue that war originated in the hunter-gatherer past. Keith Henson proposes that future outlook, memes and behavioral switches account for the origin of wars. Often two different leaders or governing bodies have a disagreement and get other men to fight for them - even if those fighting have no vested interest in the issues fought over. The original cause of war is not always known. Wars may be prosecuted simultaneously in one or more different theaters. Within each theater, there may be one or more consecutive military campaigns. Individual actions of war within a specific campaign are traditionally called battles, although this terminology is not always applied to contentions in modernity involving aircraft, missiles or bombs alone in the absence of ground troops or naval forces.
The factors leading to war are often complicated and due to a range of issues. Where disputes arise over issues such as territory, sovereignty, resource, or ideology, and a peaceable resolution fails, is not sought, or is thwarted, war often results.
A war may begin following an official declaration of war in the case of international war, although this has not always been observed either historically or currently, nor in the case of civil wars. A declaration of war is not normally made in internal wars.
 Conduct of war
The exact conduct of war will depend to a great extent upon its objectives, which may include factors such as the seizure of territory, the annihilation of a rival state, the destruction of the enemy's ability to prosecute military action, the subjugation of another people or recognition of one's own people as a separate state, or genocide. Typically any military action by one state is opposed, i.e. is countered by the military forces of one or more states. Therefore, the ultimate objective of each state becomes secondary to the immediate objective of removing or nullification of the resistance offered by the opposing military forces. This may be accomplished variously by out-outmaneuvering them, by destroying them in open battle, by causing them to desert or surrender, or to be destroyed by indirect action such as pestilence and starvation.
 Factors leading to war
"It is of course well known that the only source of war is politics ... war is simply a continuation of political intercourse, with the addition of other means." - Carl von Clausewitz, Vom Kriege (On War)
The basic motivation, of course, is willingness to wage war, but motivations may be analysed specifically. Motivations for war may be different for those ordering the war than for those undertaking the war. For a state to prosecute a war it must have the support of its leadership, its military forces, and the population. For example, in the third Punic War, Rome's leaders may have wished to make war with Carthage for the purpose of annihilating a resurgent rival; the army may have wished to make war with Carthage to exploit the great opportunity for plunder while levelling the city of Carthage. But the Roman people may have tolerated the war with Carthage on account of the demonisation of the Carthaginians in popular culture, since there had been rumors of child sacrifice. Since many people are involved, a war may acquire a life of its own -- from the confluences of many different motivations. Various theories have been presented historically to explain the causes of war:
 Historical theories
Historians tend to be reluctant to look for sweeping explanations for all wars. A.J.P. Taylor famously described wars as being like traffic accidents. There are some conditions and situations that make them more likely, but there can be no system for predicting where and when each one will occur. Social scientists criticize this approach, arguing that at the beginning of every war some leader makes a conscious decision, and that they cannot be seen as purely accidental. Still, one argument to this might be that there are few, if any, "pure" accidents. One may be able to find patterns which hold at least some degree of reliability, but because war is a collective of human intentions, some potentially quite fickle, it is very difficult to create a concise prediction system.
 Psychological theories
Psychologists such as E.F.M. Durban and John Bowlby have argued that human beings, especially men, are inherently violent. While this violence is repressed in normal society, it needs the occasional outlet provided by war. This combines with other notions such as displacement, where a person transfers their grievances into bias and hatred against other ethnic groups, nations, or ideologies. While these theories may have some explanatory value about why wars occur, they do not explain when or how they occur. In addition, they raise the question why there are sometimes long periods of peace and other eras of unending war. Nor do they explain the existence of certain human cultures completely devoid of war. If the innate psychology of the human mind is unchanging, these variations are inconsistent. A solution adapted to this problem by militarists such as Franz Alexander is that peace does not really exist. Periods that are seen as peaceful are actually periods of preparation for a later war or when war is suppressed by a state of great power, such as the Pax Britannica.
If war is innate to human nature, as is presupposed by many psychological theories, then there is little hope of ever escaping it. One alternative is to argue that war is only, or almost only, a male activity, and if human leadership were in female hands, wars would not occur. This theory has played an important role in modern feminism. Critics, of course, point to various examples of female political leaders who had no qualms about using military force, such as Margaret Thatcher, Indira Gandhi or Golda Meir.
Other psychologists have argued that while human temperament allows wars to occur, this only happens when mentally unbalanced people are in control of a nation. This school of thought argues leaders that seek war such as Napoleon, Hitler, and Stalin were mentally abnormal, but fails to explain the thousands of free and presumably sane men who wage wars on their behalf.
A distinct branch of the psychological theories of war are the arguments based on evolutionary psychology. This school tends to see war as an extension of animal behaviour, such as territoriality and competition. However, while war has a natural cause, the development of technology has accelerated human destructiveness to a level that is irrational and damaging to the species. Humans have similar instincts to that of a chimpanzee but overwhelmingly more power. The earliest advocate of this theory was Konrad Lorenz. These theories have been criticised by scholars such as John G. Kennedy, who argue that the organised, sustained war of humans differs more than just technologically from the territorial fights between animals. Ashley Montagu strongly denies such universalistic instinctual arguments, pointing out that social factors and childhood socialisation are important in determining the nature and presence of warfare. Thus while human aggression may be a universal occurrence, warfare is not and would appear to have been a historical invention, associated with certain types of human societies. Others have attempted to explain the psychological reasoning behind the human tendency for warring as a joined effort of a class of higher intelligence beings at participating in, experiencing and attempting to control the ultimate fate of each human, death.
In the fictional book Nineteen-Eighty-Four, author George Orwell talks about a state of constant war being used as one of many ways to distract people. War inspires fear and hate among the people of a nation, and gives them a "legitimate" enemy upon whom they can focus this fear and hate. Thus the people are prevented from seeing that their true enemy is in fact their own repressive government. By this theory war is another "opiate of the masses" by which a state controls its people and prevents revolution.
The Italian psychoanalyst Franco Fornari, a follower of Melanie Klein, thought that war was the paranoid or projective “elaboration” of mourning. (Fornari 1975). Our nation and country play an unconscious maternal role in our feelings, as expressed in the term “motherland.” Fornari thought that war and violence develop out of our “love need”: our wish to preserve and defend the sacred object to which we are attached, namely our early mother and our fusion with her. For the adult, nations are the sacred objects that generate warfare. Fornari focused upon sacrifice as the essence of war: the astonishing willingness of human beings to die for their country, to give over their bodies to their nation. Fornari called war the “spectacular establishment of a general human situation whereby death assumes absolute value.” We are sure that the ideas for which we die must be true, because “death becomes a demonstrative process.”
 Anthropological theories
Several anthropologists take a very different view of war. They see it as fundamentally cultural, learned by nurture rather than nature. Thus if human societies could be reformed, war would disappear. To this school the acceptance of war is inculcated into each of us by the religious, ideological, and nationalistic surroundings in which we live.
Many anthropologists also see no links between various forms of violence. They see the fighting of animals, the skirmishes of hunter-gatherer tribes, and the organized warfare of modern societies as distinct phenomena each with their own causes. Theorists such as Ashley Montagu emphasize the top-down nature of war, that almost all wars are begun not by popular pressure but by the whims of leaders, and that these leaders also work to maintain a system of ideological justifications for war.
 Sociological theories
Sociology has long been very concerned with the origins of war, and many thousands of theories have been advanced, many of them contradictory. Sociology has thus divided into a number of schools. One, the Primat der Innenpolitik (Primacy of Domestic Politics) school based on the works of Eckart Kehr and Hans-Ulrich Wehler, sees war as the product of domestic conditions, with only the target of aggression being determined by international realities. Thus World War I was not a product of international disputes, secret treaties, or the balance of power but a product of the economic, social, and political situation within each of the states involved.
This differs from the traditional Primat der Aussenpolitik (Primacy of Foreign Politics) approach of Carl von Clausewitz and Leopold von Ranke that argues it is the decisions of statesmen and the geopolitical situation that leads to war.
 Demographic theories
Demographic theories can be grouped into two classes, malthusian theories and youth bulge theories.
Malthusian theories see a misproportion of expanding population and scarce food as a source of violent conflict. Youth Bulge theory differs in that it identifies a disproportion between the number of well educated, well fed angry "fighting age" young males (2nd, 3rd, and 5th sons) and the number of positions available to them in society as a primary source of different forms of social unrest (including war). According to this view, "people beg for food, for positions they shoot."
Pope Urban II in 1095, on the eve of the First Crusade, wrote, "For this land which you now inhabit, shut in on all sides by the sea and the mountain peaks, is too narrow for your large population; it scarcely furnishes food enough for its cultivators. Hence it is that you murder and devour one another, that you wage wars, and that many among you perish in civil strife. Let hatred, therefore, depart from among you; let your quarrels end. Enter upon the road to the Holy Sepulcher; wrest that land from a wicked race, and subject it to yourselves."
This is one of the earliest expressions of what has come to be called the Malthusian theory of war, in which wars are caused by expanding populations and limited resources. Thomas Malthus (1766–1834) wrote that populations always increase until they are limited by war, disease, or famine.
This theory is thought by Malthusians to account for the relative decrease in wars during the past fifty years, especially in the developed world, where advances in agriculture have made it possible to support a much larger population than was formerly the case, and where birth control has dramatically slowed the increase in population.
Contributors to the development of youth bulge theory include French sociologist Gaston Bouthoul, U.S. Sociologist Jack A. Goldstone, U.S. Political Scientist Gary Fuller, and German sociologist Gunnar Heinsohn. Samuel Huntington has modified his Clash of Civilizations theory by using youth bulge theory as its foundation:
"I don’t think Islam is any more violent than any other religions, and I suspect if you added it all up, more people have been slaughtered by Christians over the centuries than by Muslims. But the key factor is the demographic factor. Generally speaking, the people who go out and kill other people are males between the ages of 16 and 30".
Youth Bulge theories represent a relatively recent development but seem to become more influential in guiding U.S. foreign policy and military strategy as both Goldstone and Fuller have acted as consultants to the U.S. Government. CIA Inspector General John L. Helgerson referred to youth bulge theory in his 2002 report "The National Security Implications of Global Demographic Change".
According to Heinsohn, who has proposed youth bulge theory in its most generalized form, a youth bulge occurs when 30 to 40 percent of the males of a nation belong to the "fighting age" cohorts from 15 to 29 years of age. It will follow periods with average birth rates as high as 4-8 children per woman with a 15-29 year delay. If an average birth rate of 2,1 represents a situation of in which the son will replace the father, the daughter the mother, 4-8 children per mother imply 2-4 sons. Consequently, one father has to leave not 1, but 2 to 4 social positions (jobs) to give all his sons a perspective for life, which is usually hard to achieve. Since respectable positions cannot be increased at the same speed as food, textbooks and vaccines, many "angry young men" find themselves in a situation that tends to escalate their adolescent anger into violence: they are
- demographically superfluous,
- might be out of work or stuck in a menial job, and
- often have no access to a legal sex life before a career can earn them enough to provide for a family.
The combination of these stress factors according to Heinsohn usually heads for six different exits:
- Emigration ("non violent colonization")
- Violent Crime
- Rebellion or putsch
- Civil war and/or revolution
- Genocide (to take over the positions of the slaughtered)
- Conquest (violent colonization, frequently including genocide abroad).
Religions and ideologies are seen as secondary factors that are being used to legitimate violence, but will not lead to violence by itself if no youth bulge is present. Consequently, youth bulge theorists see both past "Christianist" European colonialism / imperialism and today's "Islamist" civil unrest / terrorism as results of high birth rates producing youth bulges.
While the security implications of rapid population growth have been well known since the publication of the National Security Study Memorandum 200 in 1974, neither the U.S. nor the WHO have actively implemented preventive measures to control population growth to avert the terror threat it is now facing. Prominent demographer Stephen D. Mumford attributes this to the influence of the Catholic Church
Youth Bulge theory has been subjected to statistical analysis by the World Bank, Population Action International, and the Berlin Institute for Population and Development. It has been criticized for promoting racial, gender and age discrimination. It was also contradicted by the post-World War II Baby Boom, which saw great opposition to war amongst the so-called Youth Bulge (See Youth culture).
 Evolutionary psychology theories
Wars are seen as the result of evolved psychological traits that are turned on by either being attacked or by a population perception of a bleak future. The theory accounts for the IRA going out of business, but leads to a dire view of current wars. Studies of endemic violence and tribal warfare in the Highlands of Papua New Guinea demonstrate that intertribal warfare is highest in those parts of the country where population densities are greatest and pressure on land and other resources is thereby maximized. Similarly, evidence of organized warfare in the Ancient World, in pre-dynastic Mesopotamia and in Ancient Egypt, suggests that organized systematic warfare only appeared after population densities had increased, and there was increased pressure upon limited ecological resources.
 Rationalist theories
Rationalist theories of war assume that both sides to a potential war are rational, which is to say that each side wants to get the best possible outcome for itself for the least possible loss of life and property to its own side. Given this assumption, if both countries knew in advance how the war would turn out, it would be better for both of them to just accept the post-war outcome without having to actually pay the costs of fighting the war. This is based on the notion, generally agreed to by almost all scholars of war since Carl von Clausewitz, that wars are reciprocal, that all wars require both a decision to attack and also a decision to resist attack. Rationalist theory offers three reasons why some countries cannot find a bargain and instead resort to war: issue indivisibility, information asymmetry with incentive to deceive, and the inability to make credible commitments.
Issue indivisibility occurs when the two parties cannot avoid war by bargaining because the thing over which they are fighting cannot be shared between them, only owned entirely by one side or the other. Religious issues, such as control over the Temple Mount in Jerusalem, are more likely to be indivisible than economic issues.
A bigger branch of the theory, advanced by scholars of international relations such as Geoffrey Blainey, is the problem of information asymmetry with incentives to misrepresent. The two countries may not agree on who would win a war between them, or whether victory would be overwhelming or merely eked out, because each side has military secrets about its own capabilities. They will not avoid the bargaining failure by sharing their secrets, since they cannot trust each other not to lie and exaggerate their strength to extract more concessions. For example, Sweden made efforts to deceive Nazi Germany that it would resist an attack fiercely, partly by playing on the myth of Aryan superiority and by making sure that Hermann Göring only saw elite troops in action, often dressed up as regular soldiers, when he came to visit.
Intelligence gathering may sometimes, but not always, mitigate this problem. For example, the Argentinian dictatorship knew that the United Kingdom had the ability to defeat them, but their intelligence failed them on the question of whether the British would use their power to resist the annexation of the Falkland Islands. The American decision to enter the Vietnam War was made with the full knowledge that the communist forces would resist them, but did not believe that the guerrillas had the capability to long oppose American forces.
Thirdly, bargaining may fail due to the states' inability to make credible commitments. In this scenario, the two countries might be able to come to a bargain that would avert war if they could stick to it, but the benefits of the bargain will make one side more powerful and lead it to demand even more in the future, so that the weaker side has an incentive to make a stand now.
Rationalist explanations of war can be critiqued on a number of grounds. The assumptions of cost-benefit calculations become dubious in the most extreme genocidal cases of World War II, where the only bargain offered in some cases was infinitely bad. Rationalist theories typically assume that the state acts as a unitary individual, doing what is best for the state as a whole; this is problematic when, for example, the country's leader is beholden to a very small number of people, as in a personalistic dictatorship. Rationalist theory also assumes that the actors are rational, able to accurately assess their likelihood of success or failure, but the proponents of the psychological theories above would disagree.
Rationalist theories are usually explicated with game theory, for example, the Peace War Game, not a wargame as such, rather a simulation of economic decisions underlying war.
Genghis Khan's empire over time
An iterated game originally played in academic groups and by computer simulation for years to study possible strategies of cooperation and aggression. As peace makers became richer over time it became clear that making war had greater costs than initially anticipated. The only strategy that acquired wealth more rapidly was a "Genghis Khan", a constant aggressor making war continually to gain resources. This led to the development of the "provokable nice guy" strategy, a peace-maker until attacked. Multiple players continue to gain wealth cooperating with each other while bleeding the constant aggressor. Such actions led in essence to the development of the Hanseatic League for trade and mutual defense following centuries of Viking depredation.
Hanseatic trade and defense routes
A variation of the iterated prisoner's dilemma in which the decisions (Cooperate, Defect) are replaced by (Peace, War). Strategies remain the same with reciprocal altruism, "Tit for Tat", or "provokable nice guy" as the best deterministic one. This strategy is simply to make peace on the first iteration of the game; after that, the player does what is his opponent did on the previous move. A slightly better strategy is "Tit for Tat with forgiveness". When the opponent makes war, on the next move, the player sometimes makes peace anyway, with a small probability. This allows for occasional escape from wasting cycles of retribution. "Tit for Tat with forgiveness" is best when miscommunication is introduced, when one's move is incorrectly reported to the opponent. A typical payoff matrix for two players (A, B) of one iteration of this game is:
||( 2, 2)
||( 0, 3)
||( 3, 0)
||( 1, 1)
Here a player's resources have a value of 2, half of which must be spent to wage war. In this case, there exists a Nash equilibrium, a mutually best response for a single iteration, here (War, War), by definition heedless of consequences in later iterations. The concept is named for its originator, John Forbes Nash, about whom a book and popular film were produced. "Provokable nice guy's" optimality depends on iterations. How many are necessary is likely tied to the payoff matrix and probabilities of choosing.
 Economic theories
Another school of thought argues that war can be seen as an outgrowth of economic competition in a chaotic and competitive international system. In this view wars begin as a pursuit of new markets, of natural resources, and of wealth. Unquestionably a cause of some wars, from the empire building of Britain to the 1941 Nazi invasion of the Soviet Union in pursuit of oil, this theory has been applied to many other conflicts. It is most often advocated by those to the left of the political spectrum, who argue such wars serve the interests of the wealthy but are fought by the poor. Some to the right of the political spectrum may counter that poverty is relative and one poor in one country can be relatively wealthy in another. Such counter arguments become less valid as the increasing mobility of capital and information level the distributions of wealth worldwide, or when considering that it is relative, not absolute, wealth differences that may fuel wars. There are those on the extreme right of the political spectrum who provide support, fascists in particular, by asserting a natural right of the strong to whatever the weak cannot hold by force. Some very important centrist, capitalist, world leaders, including Presidents of the United States and US Generals, expressed support for an econonic view of war.
"Is there any man, is there any woman, let me say any child here that does not know that the seed of war in the modern world is industrial and commercial rivalry?" - Woodrow Wilson, September 11, 1919, St. Louis.
"I spent 33 years and four months in active military service and during that period I spent most of my time as a high class muscle man for Big Business, for Wall Street and the bankers. In short, I was a racketeer, a gangster for capitalism." - simultaneously highest ranking and most decorated Marine (including two Medals of Honor) Major General Smedley Butler (also a GOP primary candidate for Senate) 1935.
"In the councils of government, we must guard against the acquisition of unwarranted influence, whether sought or unsought, by the military-industrial complex. The potential for disastrous rise of misplaced power exists and will persist." - Dwight Eisenhower, Farewell Address, Jan. 17, 1961.
 Marxist theories
The Marxist theory of war argues that all war grows out of the class war. It sees wars as imperial ventures to enhance the power of the ruling class and divide the proletariat of the world by pitting them against each other for contrived ideals such as nationalism or religion. Wars are a natural outgrowth of the free market and class system, and will not disappear until a world revolution occurs.
 Political science theories
The statistical analysis of war was pioneered by Lewis Fry Richardson following World War I. More recent databases of wars and armed conflict have been assembled by the Correlates of War Project, Peter Brecke and the Uppsala Department of Peace and Conflict Research.
There are several different international relations theory schools. Supporters of realism in international relations argue that the motivation of states is the quest for (mostly) military and economic power or security. War is one tool in achieving this goal.
One position, sometimes argued to contradict the realist view, is that there is much empirical evidence to support the claim that states that are democracies do not go to war with each other, an idea known as the democratic peace theory. Other factors included are difference in moral and religious beliefs, economical and trade disagreements, declaring independence, and others.
Another major theory relating to power in international relations and machtpolitik is the Power Transition theory, which distributes the world into a hierarchy and explains major wars as part of a cycle of hegemons being destabilized by a great power which does not support the hegemons control.
 Types of war and warfare
 By cause
Marxism, succeeded by the Soviet ideology, distinguished the just and unjust war. Just war was considered to be slave rebellions or national liberation movements, while the second type carried the imperialistic character. Smaller armed conflicts are often called riots, rebellions, coups, etc.
When one country sends armed forces to another, allegedly to restore order or prevent genocide or other crimes against humanity, or to support a legally recognised government against insurgency, that country sometimes refers to it as a police action. This usage is not always recognised as valid, however, particularly by those who do not accept the connotations of the term.
"Conventional warfare" describes either:
- A war between nation-states
- War where nuclear or biological weapons are not used
(Compare with unconventional warfare and nuclear warfare.)
A war where the forces in conflict belong to the same country or empire or other political entity is known as a civil war. Asymmetrical warfare is a conflict between two populations of drastically different levels of military mechanisation. This type of war often results in guerrilla tactics. The Israeli-Palestinian conflict is a common example of asymmetrical warfare.
Military action produces a very small percentage of air pollution emissions. Intentional air pollution in combat is one of a collection of techniques collectively called chemical warfare. Poison gas as a chemical weapon was principally used during World War I, and resulted in an estimated 91,198 deaths and 1,205,655 injuries. Various treaties have sought to ban its further use. Non-lethal chemical weapons, such as tear gas and pepper spray, are widely used.
 By style
Historian Victor Davis Hanson has claimed there exists a unique "Western Way of War", in an attempt to explain the military successes of Western Europe. It originated in Ancient Greece, where, in an effort to reduce the damage that warfare has on society, the city-states developed the concept of a decisive pitched battle between heavy infantry. This would be preceded by formal declarations of war and followed by peace negotiations. In this system constant low-level skirmishing and guerrilla warfare were phased out in favour of a single, decisive contest, which in the end cost both sides less in casualties and property damage. Although it was later perverted by Alexander the Great, this style of war initially allowed neighbours with limited resources to coexist and prosper.
He argues that Western-style armies are characterised by an emphasis on discipline and teamwork above individual bravado. Examples of Western victories over non-Western armies include the Battle of Marathon, the Battle of Gaugamela, the Siege of Tenochtitlan, and the defence of Rorke's Drift.
 Warfare environment
The environment in which a war is fought has a significant impact on the type of combat which takes place, and can include within its area different types of terrain. This in turn means that soldiers have to be trained to fight in a specific types of environments and terrains that generally reflects troops' mobility limitations or enablers. These include:
 History of war
There is little agreement about the origins of war (Otterbein 2004). Some believe war has always been with us; others stress the lack of clear evidence for war in our prehistoric past, and the fact that many peaceful, non-military societies have and still do exist (See Otterbein, Fry and Kelly in bibliography below).
Originally war likely consisted of small-scale raiding. Since the rise of the state some 5000 years ago, military activity has occurred over much of the globe. The advent of gunpowder and the acceleration of technological advances led to modern warfare.
The Human Security Report 2005 has documented a significant decline in the number and severity of armed conflicts since the end of the Cold War in the early 1990s.
 Morality of war
Throughout history war has been the source of serious moral questions. Although many ancient nations and some more modern ones viewed war as noble, over the sweep of history, concerns about the morality of war have gradually increased. Today, war is generally seen as undesirable and, by some, morally problematic. At the same time, many view war, or at least the preparation and readiness and willingness to engage in war, as necessary for the defense of their country. Pacifists believe that war is inherently immoral and that no war should ever be fought.
The negative view of war has not always been held as widely as it is today. Many thinkers, such as Heinrich von Treitschke, saw war as humanity's highest activity where courage, honour, and ability were more necessary than in any other endeavour. At the outbreak of World War I, the writer Thomas Mann wrote, "Is not peace an element of civil corruption and war a purification, a liberation, an enormous hope?" This attitude has been embraced by societies from Sparta and Rome in the ancient world to the fascist states of the 1930s. The defeat and repudiation of the fascist states and their militarism in the Second World War, the shock of the first use of nuclear weapons, and an increasing belief in the value of individual life (as enshrined in the concept of human rights, for example) have contributed to the current view of war.
Today, some see only just wars as legitimate, and believe that it is the responsibility of world organizations such as the United Nations to oppose wars of unjust aggression. International Law recognizes only two cases for a legitimate war:
- Wars of defense: when one nation is attacked by an aggressor, it is considered legitimate for a nation to defend itself against the aggressor.
- Wars sanctioned by the UN Security Council: when the United Nations as a whole acts as a body against a certain nation. Examples include various "Peace keeping" operations around the world.
The subset of international law known as the law of war or international humanitarian law also recognises regulations for the conduct of war, including the Geneva Conventions governing the legitimacy of certain kinds of weapons, and the treatment of prisoners of war. Cases where these conventions are broken are considered War Crimes, and since the Nuremburg Trials at the end of World War II the international community has established a number of tribunals to try such cases.
 Factors ending a war
Conquest, stalemate, penury, famine, epidemic, bankruptcy, truce, peace, wisdom ...
Abraham Lincoln's comment to Thaddeus Stevens when Stevens shouted, "Enemies are to be destroyed!". The president responded, "Mr. Stevens, are not our enemies destroyed when we make them our friends?"
The political and economic circumstances in the peace that follows war usually depends on the "facts on the ground". Where evenly matched adversaries decide that the conflict has resulted in a stalemate, they may cease hostilities to avoid further loss of life and property. They may decide to restore the antebellum territorial boundaries, redraw boundaries at the line of military control, or negotiate to keep or exchange captured territory. Negotiations between parties involved at the end of a war often result in a treaty, such as the Treaty of Versailles of 1919, which ended the First World War.
A warring party that surrenders may have little negotiating power, with the victorious side either imposing a settlement or dictating most of the terms of any treaty. A common result is that conquered territory is brought under the dominion of the stronger military power. An unconditional surrender is made in the face of overwhelming military force as an attempt to prevent further harm to life and property. For example, the Empire of Japan gave an unconditional surrender to the Allies in World War II after the atomic bombings of Hiroshima and Nagasaki (see Surrender of Japan), the preceding massive strategic bombardment of Japan and declaration of war and the immediate invasion of Manchuria by the Soviet Union. A settlement or surrender may also be obtained through deception or bluffing.
Many other wars, however, have ended in complete destruction of the opposing territory, such as the Battle of Carthage of the Third Punic War between the Phoenician city of Carthage and Ancient Rome in 149 BC. In 146 BC the Romans burned the city, enslaved its citizens, and razed the buildings.
Some wars or war-like actions end when the military objective of the victorious side has been achieved. Others do not, especially in cases where the state structures do not exist, or have collapsed prior to the victory of the conqueror. In such cases, disorganised guerilla warfare may continue for a considerable period. In cases of complete surrender conquered territories may be brought under the permanent dominion of the victorious side. A raid for the purposes of looting may be completed with the successful capture of goods. In other cases an aggressor may decide to end hostilities to avoid continued losses and cease hostilities without obtaining the original objective, such as happened in the Iran-Iraq War.
Some hostilities, such as insurgency or civil war, may persist for long periods of time with only a low level of military activity. In some cases there is no negotiation of any official treaty, but fighting may trail off and eventually stop after the political demands of the belligerent groups have been reconciled, a political settlement has been negotiated, or combatants are gradually killed or decide the conflict is futile.
"Only the dead have seen the end of war." - George Santayana
- ^ Turnbull, Colin (1987), "The Forest People" (Touchstonbe Books)
- ^ Lorenz, Konrad "On Aggression" (Oxford University Press)
- ^ Montagu, Ashley (1976), "The Nature of Human Aggression" (Oxford University Press)
- ^ Bouthoul, Gaston: "L`infanticide différé" (deferred infanticide), Paris 1970
- ^ Goldstone, Jack A.: "Revolution and Rebellion in the Early Modern World", Berkeley 1991; Goldstone, Jack A.: "Population and Security: How Demographic Change can Lead to Violent Conflict", 
- ^ Fuller, Gary: "The Demographic Backdrop to Ethnic Conflict: A Geographic Overwiew", in: CIA (Ed.): "The Challenge of Ethnic Conflict to National and International Order in the 1990s", Washington 1995, 151-154
- ^ Fuller, Gary (2004): "The Youth Crisis in Middle Eastern Society"
- ^ Fuller, Gary (2003): "The Youth Factor: The New Demographics of the Middle East and the Implications for U.S. Policy"
- ^ Gunnar Heinsohn (2003): "Söhne und Weltmacht: Terror im Aufstieg und Fall der Nationen" ("Sons and Imperial Power: Terror and the Rise and Fall of Nations"), Zurich 2003), available online as free download (in German) 
- ^ ‘So, are civilizations at war?’, Interview with Samuel P. Huntington by Michael Steinberger, The Observer, Sunday October 21, 2001.
- ^ Helgerson, John L. (2002): "The National Security Implications of Global Demographic Trends"
- ^ Heinsohn, G.(2006): "Demography and War." 
- ^ Heinsohn, G.(2005): "Population, Conquest and Terror in the 21st Century." 
- ^ National Security Study Memorandum 200 (NSSM 200) - April 1974
- ^ Stephen D. Mumford: The Life and Death of NSSM 200: How the Destruction of Political Will Doomed a U.S. Population Policy
- ^ Urdal, Henrik (2004): "The Devil in the Demographics: The Effect of Youth Bulges on Domestic Armed Conflict," ,
- ^ Population Action International: "The Security Demographic: Population and Civil Conflict after the Cold War"
- ^ Kröhnert, Steffen (2004): "Jugend und Kriegsgefahr: Welchen Einfluss haben demografische Veränderungen auf die Entstehung von Konflikten?" 
- ^ Hendrixson, Anne: "Angry Young Men, Veiled Young Women: Constructing a New Population Threat" 
- ^ Fearon, James D. 1995. "Rationalist Explanations for War." International Organization 49, 3: 379-414. 
- ^ Powell, Robert. 2002. "Bargaining Theory and International Conflict." Annual Review of Political Science 5: 1-30.
- ^ Shy, O., 1996, Industrial Organization: Theory and Applications, Cambridge, Mass.: The MIT Press.
- ^ from conversation with NCSU Professor of Sociology Kay M. Troost
- ^ Industrial Organization - economics lecture in which the Peace War Game is an example.
- ^ The Papers of Woodrow Wilson, Arthur S. Link, ed. (Princeton, N.J.: Princeton University Press, 1990), vol. 63, pp. 45–46.
- ^ 1935 issue of "the non-Marxist, socialist" magazine, Common Sense.
- ^ George Santayana, Soliloquy #25, "Tipperary", Soliloquies in England, Scribners, 1924, p. 102
has a collection of quotations related to:
- Angelo Codevilla and Paul Seabury, War: Ends and Means (Potomac Books, Revised second edtion by Angelo Codevilla, 2006) ISBN-X
- Angelo M. Codevilla, No Victory, No Peace (Rowman and Littlefield, 2005) ISBN
- Fry, Douglas P., 2005, The Human Potential for Peace: An Anthropological Challenge to Assumptions about War and Violence, Oxford University Press.
- Gat, Azar 2006 War in Human Civilization, Oxford University Press.
- Gunnar Heinsohn, Söhne und Weltmacht: Terror im Aufstieg und Fall der Nationen ("Sons and Imperial Power: Terror and the Rise and Fall of Nations"), Orell Füssli (September 2003), ISBN, available online as free download (in German)
- Fabio Maniscalco, (2007). World Heritage and War - monographic series "Mediterraneum", vol. VI. Massa, Naples. ISBN.
- Kelly, Raymond C., 2000, Warless Societies and the Origin of War, University of Michigan Press.
- Small, Melvin & Singer, David J. (1982). Resort to Arms: International and Civil Wars,. Sage Publications. ISBN.
- Otterbein, Keith, 2004, How War Began. Texas A&M University Press.
- Turchin, P. 2005. War and Peace and War: Life Cycles of Imperial Nations. New York, NY: Pi Press. ISBN
- Van Creveld, Martin The Art of War: War and Military Thought London: Cassell, Wellington House | year=2000 | id=ISBN}}
- Fornari, Franco (1974). The Psychoanalysis of War. Tr. Alenka Pfeifer. Garden City, New York: Doubleday Anchor Press. ISBN: . Reprinted (1975) Bloomington: Indiana University Press. ISBN
 See also
 Military knowlegebase
 External links