I. Why there are always fighting in this world?
The biggest mistake that man has made is not unifying together. Dividing into big clusters engendered wars in the past. Why are humans so divided? Religion.
That's right, religion! That is the ultimate reason for the biggest sorrows in this world and it might be the biggest lying to human history.
The greatest men in this world, such as Buddha, Jesus, Mohammad,..etc., did not think that future generations would pray to them fervently as today. What they wanted was a peaceful and happy world. They had no need to stay in big temples in order to teach people at the time. They walked from places to place without any requests for their comforts from their followers. They did not want any big centers of their practices at places which New Delhi, Rome, Jerusalem,and Mecca, have established.They must be so disappointed now when they see that people have misunderstood them for so long. How many temples, churches, and mosques,...have been built in this world at direct proportional rate with human sorrows? Because they are intermediaries of the celestial and terrestrial worlds; they certainly knew that other great men would appear in this world after them, and they did not want to separate people into big clusters who worship them and who fight each other over them.
Humans from generations to generations have gone too far in wrong,and terrible ways, so that it is too difficult to fix their mistakes.
II. What might fix the problem?
Trying to expand their own clusters of religions and using force to take advantages of natural sources from other lands/clusters is not a wise idea. That is just a temporary solution to solve their problems and later on it will bring more problems to them.
To bring permanent happiness to their people, leaders of their countries need to build a good relationship with other countries. Respect, understanding, collaboration, helping each other, etc are things that we are supposed to do, not war.
Each country should reduce its defense budget to a subsistent level in keeping the peace of the country. The rest of the budget will increase education , health care , conserve/protect environment,... or relief packages for poorer countries.
Only the United Nations has the right to develop weapon, military to keep peace between countries in the world . If any country tries to disrupt the peace of the world by means of developing military power to attack other countries, then the UN will use force to punish that country and limit economic benefits on them.
Mankind is supposed to achieve a happier life together.
Similar thoughts (Philosopher Sam Harris)