Jonathan Swift explains why wars happen

"As to the first, you are to understand, that for about seventy moons past there have been two struggling parties in this empire, under the names of Tramecksan and Slamecksan, from the high and low heels of their shoes, by which they distinguish themselves.  It is alleged, indeed, that the high heels are most agreeable to our ancient constitution; but, however this be, his majesty has determined to make use only of low heels in the administration of the government, and all offices in the gift of the crown, as you cannot but observe; and particularly that his majesty’s imperial heels are lower at least by a drurr than any of his court (drurr is a measure about the fourteenth part of an inch).  The animosities between these two parties run so high, that they will neither eat, nor drink, nor talk with each other.  We compute the Tramecksan, or high heels, to exceed us in number; but the power is wholly on our side.  We apprehend his imperial highness, the heir to the crown, to have some tendency towards the high heels; at least we can plainly discover that one of his heels is higher than the other, which gives him a hobble in his gait.

Now, in the midst of these intestine disquiets, we are threatened with an invasion from the island of Blefuscu, which is the other great empire of the universe, almost as large and powerful as this of his majesty.  For as to what we have heard you affirm, that there are other kingdoms and states in the world inhabited by human creatures as large as yourself, our philosophers are in much doubt, and would rather conjecture that you dropped from the moon, or one of the stars; because it is certain, that a hundred mortals of your bulk would in a short time destroy all the fruits and cattle of his majesty’s dominions: besides, our histories of six thousand moons make no mention of any other regions than the two great empires of Lilliput and Blefuscu.  Which two mighty powers have, as I was going to tell you, been engaged in a most obstinate war for six-and-thirty moons past.

It began upon the following occasion.  It is allowed on all hands, that the primitive way of breaking eggs, before we eat them, was upon the larger end; but his present majesty’s grandfather, while he was a boy, going to eat an egg, and breaking it according to the ancient practice, happened to cut one of his fingers.  Whereupon the emperor his father published an edict, commanding all his subjects, upon great penalties, to break the smaller end of their eggs.  The people so highly resented this law, that our histories tell us, there have been six rebellions raised on that account; wherein one emperor lost his life, and another his crown.  These civil commotions were constantly fomented by the monarchs of Blefuscu; and when they were quelled, the exiles always fled for refuge to that empire.  It is computed that eleven thousand persons have at several times suffered death, rather than submit to break their eggs at the smaller end.  Many hundred large volumes have been published upon this controversy: but the books of the Big-endians have been long forbidden, and the whole party rendered incapable by law of holding employments.  During the course of these troubles, the emperors of Blefusca did frequently expostulate by their ambassadors, accusing us of making a schism in religion, by offending against a fundamental doctrine of our great prophet Lustrog, in the fifty-fourth chapter of the Blundecral (which is their Alcoran).  This, however, is thought to be a mere strain upon the text; for the words are these: ‘that all true believers break their eggs at the convenient end.’  And which is the convenient end, seems, in my humble opinion to be left to every man’s conscience, or at least in the power of the chief magistrate to determine.

Now, the Big-endian exiles have found so much credit in the emperor of Blefuscu’s court, and so much private assistance and encouragement from their party here at home, that a bloody war has been carried on between the two empires for six-and-thirty moons, with various success; during which time we have lost forty capital ships, and a much a greater number of smaller vessels, together with thirty thousand of our best seamen and soldiers; and the damage received by the enemy is reckoned to be somewhat greater than ours... "

 - from Gulliver's Travels, Part I, "A Voyage to Lilliput" (1726)