ABSTRACT
IN THIS ESSAY I examine the theoretical implications of the single most famous line from Thucydides' history of the Peloponnesian War— "What made war inevitable was the growth of Athenian power and the fear which this caused in Sparta" (1.23). 1 Realists interested in the uneven growth of power among states have been inspired by Thucydides' simple proposition. The result has been what is termed "power transition theory." In the the first part of this essay I review the strengths and limitations of power transition theory and examine how one realist scholar has utilized Thucydides' insight to devise an influential theory of hegemonic war. While realists of all persuasions lay claim to Thucydides, those realists known as power transition theorists have made the strongest case. Power transition theorists convincingly argue that the essence of Thucydides' explanation for the outbreak of the Peloponnesian War in 431 B.C. involves the shift in relative capabilities between two powerful countries. The fact that the two countries are Athens and Sparta is essentially irrelevant—it is the changing balance of power that breeds fear; this was the underlying cause of the war, and all other possible factors were contributory or distinctly secondary.
