Globalization has a huge potential for promoting peace. Historically the benefit countries could derive from war was enormous.
Alexander the Great and
Genghis Khan built massive empires through war. However the advent of nuclear weapons has made war a very expensive proposition[1]. Since the end of the Cold War globalization has further increased the expense of waging war.
Growing superpowers like China and India are so interconnected[2] with the rest of the world that a war would have devastating consequences on their economies. This economic reliance on other countries could make war an intractable prospect in the coming century.
Notes
[1]
Mutually assured destruction[2] Chapter 16 (15 in my version) of
The world is Flat (ISBN: 0-374-29279-5) by Thomas L. Friedman discusses a similar thesis.