(I remember u/vodid had a question about this a few weeks ago that I didn’t have time to answer, so I’m pinging them here.)

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What we call the First Peloponnesian War is a conflict about which we are, in the words of the late Oxford professor G.E.M. de Ste Croix, ‘exceedingly ill-informed’. Its events are known only from a very summary account in the first book of Thucydides’ Histories and a not much more detailed chronology in the universal history of Diodoros of Sicily. Thucydides’ lack of attention to this war is almost certainly intentional, and it affects not just what we know about it, but also the weird name we give it, since our entire perception of the history of fifth-century Greece is beholden to his interpretation. I’ll try to explain how this works, but first I’ll give a summary of what went down.

I’m gonna drop the “BC” in what follows so just bear in mind that the years count down to zero. Also, please bear in mind that all these dates are approximate and Wikipedia may give you slightly different dates for all these events. We just can’t tell.

 

’The cities went to war’

Up to the late 460s, Athens and Sparta were allies. Their alliance had been made to fight the Persians and had never lapsed. In 465, when a major earthquake hit Sparta and a helot revolt ensued, the Spartans called on their allies for aid and Athens duly sent a force to help. But the Spartans, for unclear reasons probably reflecting a rising tension and suspicion between the states, sent the Athenians away.

The Athenians took this as a slight, which finally gave the anti-Spartan tendency in the Athenian Assembly the upper hand against the pro-Spartan campaigners. The democracy decided it was time to rethink its position in Greek interstate politics. It rescinded its alliance with Sparta and forged a new alliance with Sparta’s ancestral enemy, Argos. This did not sit well with Sparta, which was planning a war with Argos to knock out its greatest Peloponnesian rival once and for all.

Then a war broke out over some borderlands between Corinth and Megara – both allies of Sparta – and Megara decided that if Sparta would not stop the Corinthians, it was time to abandon their alliance and find a new friend in Athens. Once this alliance was ratified in 461/0, Athens was effectively at war with Corinth. Since Corinth was a member of the Peloponnesian League, with Sparta pledged to defend it, this also meant that Athens was at war with Sparta. To the fury of the Corinthians, the Athenians promptly began building Megara some fancy new Long Walls to connect its city to the harbour at Nisaia.

A final cause for war was the fact that, when the Messenian helot rebels were finally forced to surrender under terms, the Athenians put them aboard their ships and settled them at Naupaktos on the Corinthian Gulf, stinging the pride of both Sparta and Corinth. But the sources don’t allow us to date this event securely. Either way, the Peloponnesians’ blood was up and they were ready to throw down.

As is hopefully clear from what little we know about its causes, it’s actually wrong to think of the First Peloponnesian War as a war between Athens and Sparta, like the “proper” Peloponnesian War. It was actually a war between Sparta and Argos that drew in the Athenians, and a war between Corinth and Athens that drew in the Spartans. In the early years (461-458), most of the action happened in the territory of Argos (where the Argives and Athenians won an extremely hazily attested victory against Sparta) and Corinth (where the Athenians won multiple battles against Corinth). However, the war soon spread to other areas.

In 459-8, the Athenians decided that just being at war with most of the Peloponnese and the Persian Empire wasn’t quite enough of a challenge, and invaded Aegina, which they managed to incorporate into their empire. (It was at this time that the Corinthians, thinking Athens was hopelessly overstretched, tried to capture Megara, only for Athens to send out yet another army composed only of its youngest and oldest men, and beat the Corinthians again). In 457 the Spartans marched out with a huge army to protect their alleged ancestral homeland Doris against aggression from Phokis; the Athenians and Argives confronted this army at Tanagra, but the Spartans won the pitched battle that followed. (Just to be clear, we have no tactical details for any of these battles, and have pretty much no idea how they were won or lost.)

The defeat at Tanagra caused the Athenians to lose their cool and march straight back into Boiotia, defeating the Boiotians at Oinophyta and subjecting the entire area. This was the only time in Greek history that Athens was powerful enough to subdue the whole region and add to its empire on land. At the same time, the Athenians manned a huge fleet, sailed around the Peloponnese, captured several cities, burned the dockyards of Sparta, and ravaged parts of Lakonia, the Spartan heartland.

Around 456, however, Athens suffered a major disaster: the fleet of 200 triremes that had been campaigning in Egypt this whole time was completely destroyed in a Persian counteroffensive. This seems to have brought Athens to the negotiating table, and in 453/2 a five-year truce was agreed between Athens and Sparta. During this truce, the Athenians sent a new campaign to Cyprus (451/0), but they couldn’t take the whole island. The Spartans made a separate peace with Argos, which ended up lasting the full 30 years agreed upon, taking Athens' main ally out of the war. Sparta also tried to seize control of the sanctuary at Delphi from the Phokians (449/8), but as soon as their army went home, the Athenians marched in and gave it back to them.

In 447, Athens’ fortunes collapsed entirely. Boiotia revolted, and at Koroneia a thousand Athenians were ambushed and slaughtered. When the truce ended in 447/6, Euboia revolted, and Perikles had barely crossed over to crush the rebellion when he heard that Megara had revolted too. Megara had been a key ally for Athens, because the Megarid blocked the only route from the Peloponnese to Athens by land. The Spartans, who had previously only marched to war on occasion and had never threatened Athens’ own territory, now stood on the border, ready to invade.

At this point, Perikles is said to have bribed the Spartan king to retreat from Attika, leaving his hands free to deal with Euboia. But in 446/5, with Boiotia and Megara definitively lost and Argos no longer on their side, Athens realised that things were only going to get worse for them. So they concluded a peace with Sparta that allowed them to keep Aegina, even if they were forced to give up Nisaia and the towns on the Peloponnese they had taken. The peace was supposed to last 30 years. In the end, it lasted less than 14.

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