"A More Democratic World Will Be a More Peaceful One."
Not necessarily. The well-worn observation that real democracies almost never fight each other is historically correct, but it's also true that democracies have always been perfectly willing to fight non-democracies. In fact, democracy can heighten conflict by amplifying ethnic and nationalist forces, pushing leaders to appease belligerent sentiment in order to stay in power. Thomas Paine and Immanuel Kant both believed that selfish autocrats caused wars, whereas the common people, who bear the costs, would be loath to fight. But try telling that to the leaders of authoritarian China, who are struggling to hold in check, not inflame, a popular undercurrent of nationalism against Japanese and American historical enemies. Public opinion in tentatively democratic Egypt is far more hostile toward Israel than the authoritarian government of Hosni Mubarak ever was (though being hostile and actually going to war are quite different things).
Why then do democracies limit their wars to non-democracies rather than fight each other? Nobody really knows. As the University of Chicago's Charles Lipson once quipped about the notion of a democratic peace, "We know it works in practice. Now we have to see if it works in theory!" The best explanation is that of political scientists Bruce Russett and John Oneal, who argue that three elements -- democracy, economic interdependence (especially trade), and the growth of international organizations -- are mutually supportive of each other and of peace within the community of democratic countries. Democratic leaders, then, see themselves as having less to lose in going to war with autocracies.