Why we fight?

the following was not actually written by me, I just compiled and paraphrased it...
(long read but interesting...I think)

1- war's causation must encroach into political philosophy and into discussions on a citizen's and a government's responsibility for a war.
(to what extent is the citizen morally responsible for war?), but with regards to war's causation, if man is responsible for the actual initiation of war it must be asked on whose authority is war enacted?
one may inquire who is the legal authority to declare war, then move to issues of whether that authority has or should have legitimacy.
For example, one may consider whether that authority reflects what 'the people' want (or should want), or whether the authority informs them of what they want (or should want). Are the masses easily swayed by the ideas of the élite, or do the élite ultimately pursue what the majority seeks?

2-Some claim war to be a product of man's inherited biology, theories include those that claim man to be naturally aggressive or naturally territorial, more complex analyses incorporate game theory and genetic evolution to explain the occurrence of violence and war. some accept that man's belligerent drives can be channeled into more peaceful pursuits some worry about man's lack of inherited inhibitions to fight with increasingly dangerous weapons and others claim the natural process of evolution will sustain peaceful modes of behavior over violent

3-Many who explain war's origins in man's abandonment of reason also derive their thoughts from Plato, who argues that "wars and revolutions and battles are due simply and solely to the body and its desires."
man's appetite perpetually overwhelms his reasoning capacity, which results in moral and political degeneration.
In Freud's on war ("Why War") in which he sees war's origins in the death instinct, or in Dostoyevsky's comments on man's inherent barbarity: " In every man, of course, a beast lies hidden-the beast of rage, the beast of lustful heat at the screams of the tortured victim, the beast of lawlessness let off the chain." (Brothers Karamazov, ii.V.4, "Rebellion")

4- Psychologists argue that human beings 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

5-One alternative is to argue that war is only, or almost only, a male activity and if human leadership was in female hands wars would not occur. 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

6-Other psychologists have argued that while human temperament allows wars to occur, they only do so when mentally unbalanced men are in control of a nation. This extreme school of thought argues leaders that seek war such as Napoleon, Hitler, and Stalin , and ?????, were mentally abnormal.

7-Evolutionary psychology 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.
We have the same instincts of a chimpanzee but overwhelmingly more power

8-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.

9-This theory argues that all wars are based on a lack of information.
If both sides at the outset knew the result neither would fight, the loser would merely surrender and avoid the cost in lives and infrastructure that a war would cause.
This is based on the notion that wars are reciprocal, that all wars require both a decision to attack and also a decision to resist attack.

10- AND LAST BUT NOT LEAST (the romantic answer):
Marxist theory of war, which 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.

which one applies to us?