What does one call a government which concentrates all power in the hands of thirty men? It is too small to be an oligarchy, even an extremely narrow and tight one. But it is too large to be a junta by any reasonable definition. The juntas that Lysander installed elsewhere consisted of ten men and were called decarchies (governments of ten). The government he installed in Athens appears to have been essentially the same, except with thirty men instead of ten. What is Greek for thirty? According to this link (on modern Greek), the answer is trianda. So for the lack of a better term, I will refer to the government as a triandarchy (government of thirty). The ancients called them the Thirty Tyrants, or just the Thirty. I will probably use those terms, too.
Athenian democracy did not survive defeat for long. The coup and government of thirty that followed are extremely well documented, perhaps better documented than any other event in Ancient Athens. As such they require parsing of different and sometimes contradictory sources. Classical historians emphasize the government as a Spartan imposition, while Athenian speech writers, prosecuting or defending fellow countrymen, emphasize the domestic intrigue that took place.
After Athens surrendered, Lysander sailed into port, the Long Walls were demolished, and the warships burned, as the Peloponnesians crowned themselves in victor's garlands and female entertainers celebrated with the flute. He probably then departed for Samos to continue the siege, although some sources seem to imply a single stay. Either way, the terms of the peace created an intentional ambiguity. Athens was guaranteed its ancestral government, a term deliberately vague enough that oligarchs and democrats alike could lay claim to it.
The exiles returned, eager for oligarchy and perhaps conspiring in the political "clubs" described earlier. Five men, calling themselves the Ephors after the chief executives in Sparta, apparently directed the conspiracy. The existence of these "ephors" is attested by witnesses, what they did is less clear. Aristotle seems to acknowledge some sort of conspiracy, though he denies that Theramenes had any part in it.
In any event, a meeting of the Assembly was called and Lysander was present under uncertain circumstances. Xenophon appears to date it before the Sparta forces were withdrawn. Diodorus and the speechwriter Lysias* say the oligarchs invited him. Plutarch treats it as a threat when the Athenians delayed in demolishing the walls and the new government was imposed as punishment. Aristotle merely says that he sided with the oligarchs.
What happened at the meeting is also in uncertain. Xenonphon simply says that the Assembly decided to choose thirty men to re-write the laws. He then says that Lysander sailed away to Samos and the king marched the ground forces away, so although he does not directly mention any coercion, coercion can clearly be inferred. The others are less coy. Aristotle says that when Lysander backed the oligarchs, the Assembly was intimidated and approved a decree for oligarchy introduced by Dracontides. Plutarch makes the change part of Lysander's general intimidation and identifies him as responsible for establishing the Thirty and installing a garrison, commanded by the Spartan Callibius.
Diodorus and Lysias give the most detailed accounts. According to Diodorus, it was Lysander who called the Assembly and "advised" the Athenians to choose thirty men to govern. Theramenes spoke out against him, saying that the Athenians were guaranteed their ancestral government. Lysander answered that the Athenians had broken the terms of the peace by delaying in demolishing the walls, and threatened Theramenes' life if he did not comply. Theramenes and the people then yielded, but the people elected Theramenes as one of the Thirty in hopes that he could restrain them.
Lysias' story is different altogether. He blames Theramenes for not sending for Lysander and keeping the Assembly from meeting until he was present. The Spartan commanders then called the Assembly to vote on the change in government, and no one dared oppose them. While it was Drancontides who drew up the new system of government, Theramenes was the one who proposed it to the Assembly. The Assembly raised an uproar, but Theramenes urged them to accept it, saying that many Athenians supported the new system. Lysander told the Athenians that they were in breach of the truce, that accepting the new system was the end of their freedom, but refusing it was the end of their lives. Then no one dared vote no. Some left and some refrained from voting, but all who voted, voted for the new government. The Assembly then elected ten men chosen by Theramenes, ten chosen by the ephors, and ten from among those present.
So who are we to believe? Well, four out of five say that the decision was made under duress, while Xenophon mentions no coercion, but we do not have to read very far between the lines to detect it. It seems safe to assume that the decision was coerced. Plutarch, Diodorus, and Lysias all say that Lysander accused the Athenians of breaking the truce by not tearing down the walls in time and threatened them with worse if they did not change their government. That, too, seems a safe assumption, especially since Aristotle is so sparse as not to give any details at all.
Xenophon appears to indicate that the change in government took place immediately after the surrender. Plutarch is hopeless jumbled in his chronology here, but his saying that Lysander "sent word to the people" that their time to demolish the walls had expired also seems to imply that he sailed and then returned. Diodorus and Lysias both say that Lysander had gone, the conspiracy had time to ripen, and that he then returned. Aristotle, again, is hopelessly sparse. Going with the general rule that the most detailed account is probably most accurate, I would once again lean in favor of saying that he sailed and returned.
Finally, and this will come up a lot, Theramenes' role in the Thirty is extremely controversial. Lysias' description of him is an obvious hatchet job, designed at least in part to counter some people's favorable assessment of the man. Diodorus' account, by contrast, reeks of white wash and is simply not credible in light of Theramenes' previous role in the coup by the 400. Aristotle does not have such an obvious stench, but he does try to pass Theramenes off as just another conservative politician, no different than Nicias and preferable to demagogues like Cleon and Cleophon, although he does admit that Theramenes was controversial. He does not lavish praise on Theramenes the way Diodorus does, but he misrepresents events under the Thirty to make Theramenes look good, even eliding over the fact that Theramenes was one of the Thirty at all. Xenophon's account of Theramenes during the trial of the generals is deeply hostile and not plausible. However, his account of Theramenes' conduct under the Thirty seems reasonably fair and balanced, is the most detailed of any source, and is presumably based on Xenophon's own experience, being in Athens at the time. I am therefore inclined to go with Xenophon's account of Theramenes under the Thirty more than any other.
However, I am inclined to trust Lysias on this one. Obviously Lysias would not be privy to the details of the conspiracy, and anything he said about Theramenes' role in it would be pure guess-work. The meeting of the Assembly is a different matter. As a non-citizen, he would not have been present, but he presumably heard about it from citizens, and speaking to a jury of citizens, many of whom were no doubt present or had heard accounts from people who were present, he could hardly have misrepresented such public events too egregiously. His naming of Dracontides as the one who proposed the new system is confirmed by Aristotle. And it seems far more likely that the Thirty had been chosen in advance and the vote for them was a mere facade than, as Diodorus claims, that the people chose Theramenes to be one of the Thirty because they saw him as their champion.
I will concede Diodorus one point here. The Athenians may have looked to Theramenes for leadership at this time. It is hard to say. On the one hand, he took part in the earlier overthrow of the democracy. On the other hand, he also took part in the restoration and won important battles afterward. The Athenians' continued ambivalence is revealed in the final year of the war. After executing six generals and seeing two flee into exile, the Athenians elected Theramenes, then rejected him on examination as politically unreliable. Certainly he would not have been anybody's first choice. But with the 406 B.C. batch of generals except Conon executed, with the 405 B.C. batch of general except Conon killed after their defeat, with Conon choosing exile, after the execution of Cleophon and the arrest of Strombichides and Dionysodorus, Athens was seriously short on leadership. Theramenes had, after all, negotiated the peace -- a peace hardcore nationalists like Cleophon, Strombichides, or Dionysodorus might reject as disgraceful, but one most Athenians must have seen as the only alternative to starvation. And with the fearsome Lysander threatening worse consequences yet again if the government were not changed and Theramenes saying that there truly was no alternative, maybe most Athenians were prepared to give him the benefit of the doubt.
Next: Critias and the Thirty.
*Lysias was a metic (resident alien), and as such would not have been present at the Assembly, but he might have learned about what happened from citizens who were present. He was a professional speech writer who wrote many speeches for others to deliver to the Assembly and the jury courts. Many (though by no means all) of these speeches dealt with events under the Thirty. As a ghost writer, he is not necessarily expressing his own opinions. However, the speech these events are drawn from is one that he delivered himself, in prosecuting one of the Thirty for the murder of his brother. As such, we can fairly assume it expresses his own opinions.