Thucydides' classic work is a foundational text in the history of Western political thought. His narrative of the great war between Athens and Sparta in the fifth century BC is now seen as a highly sophisticated study of the nature of political power itself: its exercise and effects, its agents and victims, and the arguments through which it is defended and deployed. It is therefore increasingly read as a text in politics, international relations and political theory, whose students will find in Thucydides many striking contemporary resonances. This edition seeks to present the author and the text in their proper historical context. The new translation is particularly sensitive to the risks of anachronism, and the notes and ample reference material provide students with all the necessary historical, cultural and linguistic background they need to engage with the text on its own terms.