Thebes' Assault on Plataea

An inquiry on Theban opportunism regarding Plataea, the opening target of the Peloponnesian War, in Thucydides.

Learn more about Plataea


It was a tentative coup de main on Plataea, seven months after the declaration of war between Sparta and Athens, that marked the beginning of hostilities of the Peloponnesian War. However, the driving force behind this first offensive was neither Athens nor Sparta, but rather the Boeotian regional power of Thebes. This city had historically been at odds with Athens for control over its periphery. Thebes grew to hate Athens, its democratic ideology, and most of all its “protectorate” of Plataea, which it accused of “Atticism”.1 As such, Thebes sought to ally itself with the Peloponnesian power of Sparta, which would defend it from its Attican neighbours and, if possible, enact vengeance upon those Boeotians which would support Athens. This essay will argue that the Theban assault on Plataea was necessary, given Thebes’ geographic isolation from its Peloponnesian allies; enabled by Pericles’ defensive strategy and Spartan pressure on Athenian lands; fuelled by Thebes’ hate towards Athens and its democracy; and inspired by the territorial ambition of a unified Boeotia under Theban leadership. With these arguments, we shall conclude that Theban foreign policy was, in its essence, opportunistic — being willing to pursue its goals dishonourably while making clever use of its allies to further them.

Military considerations

To begin this assessment, we must first inquire as to why Plataea, as a military target, was of such importance. The small town of Plataea flanked the roads that connect Thebes (which was already considered a borderland of sorts) to the civilised regions of the Hellenic world. On one hand it was a small entrepôt for the goods flowing to and from Megara and the Peloponnese to Thebes, while on the other it served as a gateway from Attica to Boeotia. This meant that Plataea was an ideal Athenian forward operating base for any incursions on Theban lands, with the added benefit that it could disconnect the mostly landlocked Boeotians from their Spartan allies in the Peloponnese.2

Thebes rightfully acknowledged Plataea’s strategic significance. The mere existence of an Athenian-aligned Plataea posed an existential risk to Thebes, so long as its access to any of its allies and trade partners remained dependant on road travel due to its lack of a viable trading port of its own — making it virtually landlocked — and Athenian hegemony over the seas, both of which left Thebes dependant on the trade that flowed through the roads neighbouring Plataea. In this sense, it was necessary for Thebes to take Plataea if a war between itself and Athens broke out, and it did so with extreme prejudice.

Notwithstanding these immediate military considerations, Plataea’s tightly knit alliance with Athens, which stemmed from Plataean fears of Theban aggression3, would ordinarily mean that the Athenians would provide aid to Plataea. However, these were not ordinary times, and Pericles perceived the risk of fighting Sparta head-on to be too high to risk protecting a city of secondary importance, preferring instead to preserve his forces within the recently built Long Walls of Athens. This left those Athenian allies which had no access to the sea vulnerable, and none so more than Plataea.

By the time of its assault of Plataea, seven months since the declaration of war had passed without any noteworthy engagement between the two sides. During this “Phoney War”4 of sorts, Thebes was well aware that the Athenians, heeding to Pericles’ words, would not commit to venturing out of their walls to save tiny Plataea (with any assistance provided being token at best), however loyal to them it might have been in the past. The Thebans, then, had plenty of time to prepare their takeover of the town, which was intended to be carried out swiftly and covertly (which we know did not end up occurring). It thus becomes clear that — given the aforementioned military necessity for Theban dominance over Plataea, and the defensive posturing that its protector adopted — Thebes found itself under the ideal condition to attempt to draw first blood in the coming war.

Theban ambitions for Boeotia

Nonetheless, military expediency alone does not explain or justify an assault during what was still considered to be peacetime, particularly on a city that was not directly involved in the war, and which was considered to be protected due to its gallant display of courage before the gods, warranting a double charge of impiety by the offended party.5 Thebes was a society with its own fears and ambitions, namely regarding its immediate surroundings in Boeotia proper and those who had influence in the region. It is precisely because of said ambitions and fears that states feel pressed to go to war, and I believe such as also the case with Thebes. Being its largest city, Thebes was the centre of power of the Boeotian league, which sought to unite all of Boeotia into a cohesive and centralised authority under its dominance. However, Athenian influence in Boeotia, namely in Plataea, stood in Thebes’ way of realising its ambitions of regional hegemony.

Athens had occupied most of Boeotia during the First Peloponnesian War, just a few years prior, and Plataea embodied this blot of Athenian democracy staining Boeotia, taunting Thebes and its oligarchy by merely existing. This translated itself into a growing resentment among the Theban elite towards Athens and its democracy.

Theban opportunism

Th. is especially harsh in portraying Thebes, as we can observe in their speech (Th. 3.61-3.67). The rhetoric in this passage translates a great deal of revisionism by the Thebans regarding their causus belli in attacking Plataea, and regarding their own past of Medism, which it dismisses as senseless accusations while its government was of tyrannical contours (Th. 3.62). Simon Hornblower, however, points to the more nuanced possibility that Th. is being tendentious with his choice of words.6

Regardless, I am inclined to side with Th. in his portrayal of Thebes as opportunistic regarding Plataea, and I believe it to be a rightful description of Theban foreign policy in general. Looking back, we can see a city that in recent history sided with the Persians that sought to subjugate the whole of Hellas and, when accused of doing so, defends itself with the argument that it was then under tyrannical rule unwillingly and that Plataea is now an Athenian puppet willingly. I agree with Hornblower and his reference to Hdt. which implies that “the city’s medism was not the work of a few men”7, and that the Theban elite (before and regarding Plataea in the Peloponnesian War) consistently chose to circumvent what was considered to be honourable. This being said, the overall assessment of opportunism (which might be interpreted as realism) on Thebes’ part must be complimented with the very real strategic considerations that were taken into account regarding the dangers of an Athenian-aligned Plataea.


  • Strassler, Robert B., ed. 2008. The landmark Thucydides: a comprehensive guide to the Peloponnesian War. Free Press.
  • Kagan, Donald. 2004. The Peloponnesian War. Penguin Books.
  • Hornblower, Simon. 1991. A Commentary on Thucydides. 2003 Reprint. Vol. I. Oxford University Press.


  1. Th. 3.62.1 

  2. Kagan, p. 64 

  3. Hornblower, 2.2.1 

  4. I believe there is a certain parallel to be made regarding the similarity of this stage of the war, between the declaration of war and the first engagement in Plataea, with the Phoney War period of the Second World War. These periods lasted roughly the same time, with few to no main engagements (at least regarding the Western Front of the most recent conflict) taking place. Though such a comparison may be superficial at best, I thought it to be noteworthy. 

  5. Hornblower, 3.56.1 

  6. Hornblower 3.62.3 

  7. Hornblower 3.62.3