In a provocative study on comparative empire, noted historians identify periods of transition across history that reveal how and why empires emerge. Loren J. Samons on Athens and Arthur Eckstein on Rome examine classical Western empires. Nicholas Canny discusses the British experience, Paul Bushkovitch analyzes the case of imperial Russia, and Pamela Kyle Crossley studies Qing China's beginnings. Frank Ninkovich tackles the actions of the United States at the turn of the twentieth century, which many view as imperial behavior.

What were the critical characteristics that distinguished...