It appears that perhaps the most important way in history that communities get together and live in harmony is via commerce and cooperation.
In regions where there are constant “conflicts” such as India-Pakistan and North-South Korea, the conflicts seem to occur mainly between the governments.
The arbitrary and artificial borders which exist between India-Pakistan and North-South Korea actually broke apart several families which lived on either side of these “borders”. The people, if left to themselves, continue their family relationships, begin trading with each other and relative peace blossoms.
A precursor to trade and commerce to be successful is that property rights should be recognized and protected. Wherever this is the case, commerce and peace blossom.
For example, the Eurozone was set up ostensibly to help ease trading between the European countries. So far, this has been successful in keeping the peace in that region.
Similarly, one can visualize the United States as having achieved peace within it’s borders because of the observance of property rights and because of the constant trading that goes on between it’s states. When the original thirteen colonies got together to form the United States, there were plenty of disagreements and conflicts between the colonies. It was after a long struggle that the colonies were able to unite and form one nation.
Perhaps, a world where there are innumerable small states and communities which firmly protect property rights and carry on constant commerce with each other may be the best bet for peace.