I bought the book at a rummage sale in 1981, and I don't think I've read it until now. However, I understand international politics a smidgen better than I did 30 years ago. Another good thing about this book is that it was written and published in 1967, pretty much before Political Correctness. I reproduce the text exactly as written; I will mark any alterations I make.
From the preface:
Few events compare, in impact and terror, with World War I. It destroyed two empires, that of the Habsburgs and that of the Ottoman Sultans. It altered two others, that of the Hohenzollerns and that of the Romanovs, beyond recognition. It created a host of new nations in Europe and overseas. It gave birth to Communist rule in Russia and provided the background for Fascism in Italy and elsewhere. In its course, roughly twice as many people were killed as in all the wars of the preceding two centuries added together, the Napoleonic Wars and the American Civil War included. It also maimed, in body or spirit, many of the survivors and laid the ground for an even more destructive World War II.
But it is not the purpose of an alliance to provide a structure under which governments can grow sentimental over their sympathies for each other or exchange congratulations on the similarities of their views on life, politics, and the universe. Alliances are not friendships. If they were, we would scarcely have any, for national friendships are either illusory or very rare. (National antagonisms are a different matter.) Rather, alliances are in essence concluded so that a country may count on another to fight by its side in times of war, and to support it by a variety of other means in times of peace. A common ideology between allies is a pleasant luxury -- it will save the secretary of state from much domestic criticism -- but it is not an essential. Mutual advantage is. Common interests, and above all, a common foe, can make allies of nations whose domestic institutions are half a dozen constitutions apart.