Why do we fight wars? The cop-out answer shunts the blame to our genes invoking some genetic predisposition to aggression. It is a circular reasoning. It is innate these advocates claim because we always fight wars so it must be in our genes. That is not good science. Humans also cooperate and form communities that go beyond the family and extend to national identity. Is it in our genes then to cooperate? The same circular reasoning can be used to justify this. Also, there is no known aggregate of people who are all rugged individualists to support an alternative theory. I would use a different argument about the social construction of wars. Take the case of Sweden. Until the early middle ages they were Vikings and terrified other European shores with raids that were wantonly aggressive. After they were Christianized they shifted to wars with Russia and lost Finland to the Russians. They converted to Lutheranism during the Reformation and under King Gustav Vasa they had numerous wars against Denmark, the Baltic States, Poland, and Russia. Under Charles XII they marched their way south until they were defeated by the Russians. Charles XII returned and attacked Norway only to be killed in 1718. A century later they joined the countries fighting Napoleon’s army. From 1814 on they have not been involved in any war. There was no mega-mutation or population shift and mixture that brought this about. It was not biology but social policy of the Swedish government that rejected war and saw Sweden’s future in manufacturing and providing for the welfare of its citizens. The same can be said for the Swiss. They organized into Cantons that joined in 1386. Many of their young men made a living as mercenary soldiers hired by other countries to guard their palaces. In 1506 the Papacy employed the Swiss Guards to protect the Vatican. In 1798 the French invaded but peace was restored after Napoleon’s defeat. During the Reformation civil war broke out with Protestant against Catholic and erupted episodically until 1847 when the Swiss Republic established its constitution. Since then Switzerland has maintained its neutrality, but unlike Sweden, it chose to establish universal military training for all its males. This made the prospects of fighting Switzerland a costly one and the Swiss have enjoyed more than 150 years of peace since then.
I would argue that the biggest obstacle to a world without wars is patriotism. All countries indoctrinate their citizens, celebrate their heroes for military victories of the past, and revere those who died in fighting for their country. For some who are indoctrinated, criticism of military options for foreign policy is bordering on treason. It took a Civil War to overthrow slavery in the US which was established in the South as a way of life. It may take a world war with nuclear weapons killing half or more of the world’s population to make the survivors do what the Swedes and Swiss recognized. Living in peace is a better option than the disruptions caused by war. I hope that just as most countries gave up slavery without a civil war, a generation will emerge that looks on war as a moral failure as antiquated as rooting out and persecuting witchcraft or purchasing slaves to do hard, life shortening, or unpleasant labor.