War is, first of all, a behavior pattern that means a definite state of organized conflict between two or more social entities. The main reason for such a conflict is an attempt to be on top of hierarchy either psychological or material. Aspect of domination is basic for all wars throughout history. But all over the history war was undertaken as noble. Nowadays we can postulate war not only as undesirable but also as morally problematic issue.
Are there reasonable causes to start a war? It is obvious that the issue is deeper than it seems. Pacifists will surely announce that there are no fair reasons to start any kind of war. Other point of view lies in accepting perceived threat as possible viable reason for a war.
But in this case there are some questions to be answered. When does this threat become a serious reason for a war? What are after-effects or consequences of ignoring the upcoming threat? How much time should pass from the moment when the threat appears to the moment when actions need to be taken?
Threats also can be different. Are they life-important? In terms of war we understand threat as threat to human existence: scarce and deficient resources or incompatible ideology. The unchangeable factor for all kind of wars is the usage of organized violence and destruction of lives and property.
Anyway, injustice also develops; it also has dynamics. And the question is: should people risk their lives fighting or should they risk becoming victims?
Modern international law accepts only two types of wars: war of defense and wars that are sanctioned by UN Security Council (for example, peace keeping operations).
To sum up we’d better use words of Carl Von Clausewitz: “Every age has its own kind of war, its own limiting conditions and its own peculiar preconceptions.”