Well, International Relations came about around 1914 and at that time people thought that nations went into war for obvious reason i.e self defence and to gain something from the invaded country. But around this time, people started questioning the actual reason for war - especially since money was spent, there was a lot of negetive effects of war, such as civilian deaths etc etc. So, they came to the conclusion that International relations is the study of war, security and state. Also, in this subject there is never only one 'textbook' theory - there are many theories as to why a certain thing happened. I personally think that International Relations isnt just about state, war and security, but also about religion because without the religious element there will not be a question of war and security. An example can the second world war and the Holocaust.
Complicated. Depends how you look at it, the nations have come together for a purpose but that purpose is of no good (WAR).. Religion is system which speaks out against the elite system. That is why it's always at war. They cannot stand it that there are others who can gather the masses into believing in a totally different system...