In a fascinating, but largely overlooked book, How Enemies Become Friends,Charles A. Kupchan reviews many historical case studies of how nation-states with a long history of conflict managed eventually to become secure and peaceful friends. His examples include the formation of the Swiss Confederation (1291-1848); the creation of the Iroquois Confederation in the century or so before the first Europeans arrived in America; the establishment of the United States (1776-1789); the unification of Italy (1861), and of Germany (1871); the Norway-Sweden rapprochement (1905-1935); the formation of the United Arab Emirates (1971); and the Argentine-Brazilian rapprochement of the 1970’s.