I guess I can already see that this thread, while well-meaning has the probability of turning into some politically based quagmire. Still, I'll throw my thoughts in just because I apparently still don't know any better, and I've had maybe too much to drink.

I think that peace would be possible if people could evolve beyond the way we currently are. As long as there is a desire for power, money, or resources, there will be a driving factor for unrest. Whether it's larger, more well-endowed countries acting as 'police' of sorts in other nations or smaller nations fighting amongst themselves for power/money/resources, there will likely always be some sort of military action somewhere.
Take John Lennon's song "Imagine". I love the song, I love the ideal, but that's what it is, it's an ideal. Do you think we'd ever see a world without religion, possessions, no nationalism, no greed, no hunger, etc etc? Probably not, realistically. To go on a more evolutionarily based argument, people are not so far from the warring chimp bands in the jungles of Africa, and as long as there is an 'us' there will be a 'them', and while our motivations may be very different, the psychology of our rivalries still seems similar.
I think the ideal of peace is a good thing to work for, that one can be the change they want to see. I think if everyone tried, life could be more peaceful in much of the world. Do I think 'Peace' as a utopian existence is possible? Not the way we are now.