I think all human societal conflict stems from the belief of certain individuals or groups that they are superior to other human beings and therefore have the right to impose their view of how the world should be on everyone else. It is this arrogance that makes some people think their dealings with their fellow human beings shouldn't be on the basis of a voluntary exchange of value. Every militaristic leader in history has had this arrogance - I am better than you and I know what is best, so I should rule and you should submit. Sometimes this arrogance stems from religious faith (e.g. Christian Crusades and Muslim jihad), sometimes from philosophical dogma (e.g. Marxism), sometimes even from misguided scientific theory (e.g. Nazi eugenics). Political leadership that is based on a voluntary exchange of value - a social compact to use a modern term - does not need force because most individuals in most human societies will gladly exchange a degree of absolute freedom for a political structure that honours and preserves their individual rights.
Unfortunately we live in a world not dissimilar to that which existed immediately prior to World War One. Liberal, democratic institutions are being curtailed and politicians and bureaucrats are taking more and more power to themselves in the name of protecting us from faceless enemies. The real conflict in the first half of the Twentieth Century was not between the European powers and their far-flung allies, but between the ideas of individual freedom and mob rule. Imperialism, Communism, Nazism and Fascism have an etymological commonality - they all derive from collective nouns and are all about dictatorial rule in the name of the group.
It is freedom from mob rule that we won in two World Wars and in the Cold one, and it is this that we should honour and preserve when remembering our fallen soldiers.