The cause of great power war is a perennial issue for the student of politics. Some 2,400 years ago, in his monumental History of the Peloponnesian War, Thucydides wrote that it was the growth of Athenian power and the fear that this power inspired in Sparta which rendered the Peloponnesian War somehow necessary, inevitable, or compulsory.
In this new political psychological study of Thucydides' first book, S.N. Jaffe shows how the History's account of the outbreak of the war ultimately points toward the opposing characters of the Athenian and Spartan regimes, disclosing a Thucydidean preoccupation with the interplay between nature and convention. Jaffe explores how the character of the contest between Athens and Sparta, or how the outbreak of a particular war, can reveal Thucydides' account of the recurring human causes of war and peace. The political thought of Thucydides proves bound up with his distinctive understanding of the interrelationship of particular events and more universal themes.
The article at War on the Rocks provides an overview of the History and provides a nice summary of why it's wrong to accept Thucydides at face value when he states “the growth of the power of Athens, and the alarm (or fear) which this inspired in Sparta, made war inevitable … or necessary or compulsory.” The whole article is worth a read and I sincerely hope to read Jaffe's book for more on his interpretation. For now, here's part of the article's summary on that inevitability:
I maintain that Thucydides does not mean inevitability as efficient causation, or in any sense that suggests that the forces involved are fully external to the actors. Instead, I argue that the objective inevitability of a Peloponnesian War is in fact the product the subjective views of the actors themselves, rooted in the deeply opposing characters of Athens and Sparta, or in the ways that the cities differently privilege security, honor, and profit. To abridge a complicated story, what Thucydides means by necessity is perhaps best understood as the imperatives of the national interest, as the actor in question understands those interests, while these interests are themselves conditioned by overarching world views or disparate cultural outlooks.
To draw these threads together, a Peloponnesian war became “necessary” when the actors themselves came to see no alternative to it. This does not mean that they were correct to arrive at that decision, or that there were no alternatives to war. Instead, Thucydides illuminates the interactive chain of events by which the protagonists themselves became locked into path dependencies, firmly convinced of the reasonableness of their actions or policies, which, in fatal combination with one another, led to a mutually destructive war.
As Jaffe points out, there is "vigorous disagreement" on the study of Thucydides...what the author meant and how to apply his lessons. Whether or not you agree with Jaffe's remarks on Thucydides, his framing information should be of use to anyone wanting to read the History.