Is War Necessary?

As a person who likes to make things as uncomplicated as possible, and also, a person who likes to at least pretend that she is for the better good of all people, the obvious answer is a big, resounding, 'NO'. However, I am not a politician, my decisions don't impact millions of people, and its all very easy to figure out what I think is right when I'm sitting in a classroom.
I think that for war to truly be obsolete, every leader of every country would have to believe that it isn't necessary, which we all know is impossible. They would all have to be either master negotiators, or otherwise, very satisfiable compromisers. A politician's dream is to be able to satisfy everybody, which is impossible in almost every issue people face. Regardless of who is right and who is wrong, there will always be a group of people who will rebel, and there is always a group of people who will use force to try and get what they want. On a national scale, for a country to be completely isolated from war, they would have to simply not care about the rest of the world, which is wrong. So do I think that war is necessary? Well, I wish it wasn't, and maybe someday, it won't be, but as long as innocent peoples' lives are threatened for whatever reason (as in, a country is invading a country not for its own benefit, but because people there are dying and they aren't able to protect themselves), sometimes there is no choice but to push back.