Thucydides’ account of the Peloponnesian War continues to receive the attention of both readers and commentators, millennia after its recording, with enduring debate over the lessons contained in the text. Most recent discussion has centred around Graham Allison’s examination of the so-called Thucydides Trap, and the lessons this holds for US-China relations. While I would side with Paul Van Riper in arguing that history holds no lessons per se, in the reading of history one may come to understand the “timeless verities of combat.” Indeed, Thucydides provides little overt analysis in his account, nor does he seek to draw many concrete lessons from his record (and certainly does not himself warn of a Thucydides Trap).
Instead, the enduring importance of The History of the Peloponnesian War resides in its ability to prepare the reader to recognise historical patterns hidden in chaos regarding the human element in war. Using the model of historical study proposed by Sir Michael Howard, the span of Thucydides’ account allows the reader to study war in width and examine continuities, trends, and patterns in human behaviour in war. By incorporating both chronological events and the speeches of key decision makers into his argument, Thucydides provides an opportunity to study in depth the chaos and uncertainty inherent in war (at least to the degree that a single source can provide). Finally, by expanding his analysis to include the cultures of the societies participating in the conflict, Thucydides enables the reader to study the context within which the war was fought.
By incorporating a series of conflicts into a single account spanning decades (431-410 BCE), Thucydides offers an opportunity to consider whether war is a discontinuity in human affairs, or if instead peace is a temporary interruption to constant war. Throughout the war, multiple armistices are declared; yet war returned with a similar character to the war that preceded the peace. Following the Peace of Nicias (421 BC) conflict between Sparta and Athens continued, and the Peace was only formally abandoned in 414 BC. During this period of peace, the Battle of Mantinea, the largest land battle of the entire war, was fought in 418 BC. By continuing beyond the events of 421 BC, Thucydides demonstrates that each period of war is linked with its precursor and successor.
By framing key decisions around a debate consisting of opposing views (the technique of dissoi logoi ), Thucydides also exposes the continual uncertainty inherent in decision making in war. While fear may have encouraged Sparta’s war with Athens, the benefits of war were debated extensively (both internally and with their allies) against uncertain chances of victory. Following their victory at Pylos, Athens had an opportunity to seek peace with Sparta on favourable terms but, swayed by their leader Cleon, instead “grasped for more.” When Nicias later argued against the Sicilian expedition, that Athenians should “keep what you have and not risk it for advantages...which you may or may not attain,” his pessimism was countered by Alcibiades: “...what reason can we give to ourselves for not holding back?” The uncertainties faced by these decision makers may prepare those looking for contemporary application of Thucydides’ work to better assess the stated intended effects of a decision, the circumstances in which it was made, and the eventual outcome.
By the span and the depth of his account, Thucydides allows an examination of the limitations of human decision making when balanced against both immediate and longer-term consequences. Such an approach is in tension with the natural instinct to derive broadly applicable lessons from key moments in the account. Reading the Melian dialogue in isolation, the validity of the Athenian position (“while the strong do what they can and the weak suffer what they must”) appears strong and valid as a means of power diplomacy. This can be tested against the immediate consequences of the Athenian decision, the destruction of Melos and found equally valid. Viewed across the span of the war, however, the Athenian approach eventually triggers a growing series of revolts against their rule, conflicting with their original intent. When read widely in this manner, the text demonstrates that the consequences of actions often echo through time, beyond the limited viewpoint of the decision maker.
By providing the context of the societies engaged in the war, Thucydides’ account illuminates the role of cultural norms or principles in shaping decisions in war. For example, the debate by the Athenians, centred around Cleon and Diodotus, as to whether to recall their order to destroy Mytilene after their revolt, demonstrates an enduring question in human affairs: is consistency in action or just decision making more important. The depth of examination by Thucydides highlights that while understanding the character of its human actors is important, these actors are a product of their society––so, like the wars they fight, they are “understood only if one understands the nature of the society fighting.”
Thucydides’ account of the societies fighting provides an opportunity to examine how the stress of war can alter the strategic culture of societies. Cultural norms shape how societies organise for war and make decisions about the employment of war as a policy tool, however gradual change may be imperceptible to the actors within a society. Upon entering the war, Pericles warns against distractions and diversions in their pursuit of victory. Gradually however, following multiple years of war and the loss of Pericles himself, the Athenians leadership is worn down and grow increasingly distracted and fractured, ultimately leading to diversionary gambles such as the disastrous Sicilian expedition. Such an understanding enables greater insights into how human societies have difficulty making consistent decisions in the presence of war.
His account also demonstrates the stress placed on military cultures to adapt to best defeat the adversary. At the beginning of the conflict, Spartan land power was supreme and a core element of their society; Athens prided itself on its maritime power as a means of defeating Sparta, and avoided seeking a decisive land battle. Yet, as neither side showed signs of weakening, both were forced to adopt different ways of warfare. Thucydides himself noted the irony in the Battle of Pylos, where Athenians defended Spartan land against Spartans attacking from the sea. Thus, the Athens that finally capitulated was not defeated by the Spartan military it faced at the outset of the conflict; both had adapted in ways unforeseen at the outset of conflict.
Finally, the very character of societies and their underlying political structures can be seen to change under the stress of war throughout his account. Early in the war Athens is held up as a democratic ideal type by Pericles in his Funeral Oration, where debate was “an indispensable preliminary to any wise action.” As time passed, its ideals were slowly stripped away by the necessity of winning the war, ultimately leading to the installation of an oligarchy in an attempt to secure victory. Similarly, Thucydides demonstrates the shift in governing structures across the Hellenic world, as democracy gives way to oligarchs and then outright dictators. Thus the Athenian society that chose war in order to maintain its character was gradually and irreversibly changed by its experiences in that war, much changed from the Athens of Pericles’ time.
Thus, while highly unusual to study a war from a single source, in the breadth of his account Thucydides comes close to meeting Michael Howard’s model of studying widely, deeply, and with context. By doing so, Thucydides provides an important reminder that the human element remains at the heart of war. As such, a recognition of the enduring nature of human behaviours, their base motivations, and the difficulties and uncertainties humans face are instrumental to an understanding of war and history. From this understanding, it follows that the path to a decision is rarely clear to the decision maker, and that consequences of decisions continue to echo through time.
Rex Harrison is a Royal Australian Air Force officer. The views expressed are the author's and do not reflect the official position of the Royal Australian Air Force, the Australian Department of Defence, or the Australian Government.
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Header Image: The Plague of Athens by Michiel Sweerts (Wikimedia Commons)
 Allison, Graham. Destined for War: Can America and China Escape Thucydides’s Trap? (New York, NY: Houghton Mifflin Harcourt, 2017).
 Paul van Riper, “The relevance of history to the military profession: an American Marine’s view.” in Past as Prologue: The Importance of History to the Military Profession (Cambridge: University of Cambridge Press, 2006), 39.
 Michael Howard, “The Use and Abuse of Military History,” Parameters, Vol. XI, No. 1 (reprinted), 14.
 Thucydides, Robert B. Strassler, and Richard Crawley. 2008. The Landmark Thucydides: A Comprehensive Guide to the Peloponnesian War. New York: Free Press, 341.
 Dissoi Logoi, also called dialexis, is a two-fold argument, which considers each side of an argument in hopes of coming to a deeper truth. (http://www.niu.edu/wac/archives/files/dissoi.html)
 Thucydides, Peloponnesian War, 16.
 Ibid., 245.
 Ibid., 372.
 Ibid., 352.
 Ibid., 356.
 Ibid., 176.
 Michael Howard, “The Use and Abuse of Military History,” 9.
 Thucydides, Peloponnesian War, 83.
 Ibid., 127.
 Ibid., 230.
 Ibid., 113.
 Ibid., 512.