Any book that starts with a speech by Archidamus and the Peloponnesian War is catnip to a certain type of reader. And A. Wess Mitchell’s Great Power Diplomacy , though it competes in a crowded field, does exactly what it sets out to do: Explain how and why diplomacy has mattered over the last millennium or two—and why it really matters today. There is a grand tradition of books on diplomacy, some of which I dust but seldom. Obviously Henry Kissinger’s Diplomacy is up there. So, too, is Robert