The only reason they would not oppose war is in case of defending their country against invasion and conquest. It is probable that most people, for most of the time, believe that war may sometimes be necessary to preserve national integrity or the international order. In time of war, governments sometimes use a variety of types of propaganda to persuade their citizens that the war is just. The success of using such propaganda as reasons for war has to do with how governments play on the issues of national pride, traditions, religious beliefs and etc. Portraying the enemy as sub-human, evil and lacking in individuality helps to justify aggression against them. In other cases the leader or some other major figure is demonised. "Thus in the Gulf war, Saddam Hussein was demonised, and his soldiers seen as sharing his guilt." There will always be nations who will be tempted to exploit and manipulate weaknesses of their neighbour for easy advantage. It seems that society these days makes war look "natural" and a practical way of solving disputes.
Human nature tells us that war can never be totally eradicated for the same reason that crime, greed, poverty, violence, and sin will never be eradicated. People are capable of committing the most terrible acts of violence on other people. From before recorded history humans have killed humans, and violence is potentially present in every society. There is no denying the fact that the spark to develop a tendency for violence is part of human nature. This particular human characteristic is explained well through the theory of evolution. In the course of human evolution, belonging to a group or community could increase the ability of an individual to survive or reproduce. It is thus reasonable to assume that natural selection acted to favour behaviours that resulted in-group integration. The consequences of those selective forces still operate today.
