Aigospotamoi: the final battle of the Peloponnesian War (431-404). In September 405, the Athenians were decisively defeated by the Spartans and lost their navy. As a result, the siege and fall of Athens became inevitable.
It is too easy to accuse the Athenian state of overconfidence for rejecting the Spartan peace offer. The Athenians, however, justifiably distrusted Sparta. After all, it had previously violated a peace treaty. Besides, there was a realistic chance that Athens could turn the tables to her advantage, if she could just drive a wedge between Sparta and her ally Persia. If Athens could stay in control of the grain shipments coming in from the areas around the Black Sea, and if she did not lose her navy, the Persian will to finance Sparta could reasonably be expected to falter. Unfortunately for Athens, neither of these prerequisites was met. Lysander's decisive and aggressive preliminary man oeuvres shattered any Athenian hope for a quick victory. Athens was forced to position her fleet very unfavorably at Aigospotamoi in order to counter the Spartan threat.
Subsequently, logistical necessities forced the Athenian admirals into action, with all the disastrous consequences. Nevertheless, the defeat at Aigospotamoi is not, in my opinion, solely a result of the unfavorable position from which the Athenians were forced to give battle. Lack of trust - in their admirals and in a victory - is proved by the many rumors and accusations of treason that circulated after the defeat. This particular collective frame of mind can be supported by the Athenian belief in the following oracular statements:note[Both oracles are quoted by Pausanias, Description of Greece, 10.9.11.]
The Delphic Sybil:
And then on the Athenians will be laid grievous troubles
By Zeus the high-thunderer, whose might is the greatest,
On the warships battle and fighting,
As they are destroyed by treacherous tricks,
through the baseness of the captains.
For on the Athenians comes a wild rain
Through the baseness of their leaders, but some consolation will there be
For the defeat; they shall not escape the notice of the city,
but shall pay the penalty.
I believe it is likely that this lack of confidence already played a role before the battle of Aigospotamoi. This can be concluded, in my opinion, from the incomprehensible, or at least drastic, execution of the Athenian admirals after the battle of Arginusae. Besides, we may assume that lack of confidence acted as an incentive to desert. Lastly, a lack of confidence may explain why Athenian resistance faltered so quickly after the Spartan landing. So I believe that, besides the clever tactic of Lysander, the Athenian defeat was the result of internal lack of support. Athens was, in other words, its own enemy.
The difference in interpretation of the battle of Aigospotamoi between Xenophon and Diodorus can be explained by their different perspectives. Xenophon, who idealizes Sparta, writes from a Spartan point of view, or - perhaps more accurately phrased - from an aristocratic point of view. Besides, his friendship with king Agesilaus II of Sparta would have given him access to valuable sources. Xenophon did not hold democracy in high esteem. To him it was undisputable that the Athenian mob would elect incompetent and reckless commanders, who would not bother themselves with petty details like the provisioning of the army or the keeping together of the fleet. Therefore Xenophon did not waste any time in explaining these matters. Although Xenophon was disdainful of Lysander's populism, he did acknowledge that he was a good admiral. Naturally then, the victory over the Athenian fleet could be accredited to Lysander's qualities.
Diodorus appears to be better informed on Athenian matters and chooses a more neutral approach. He seems to strive for a well-balanced description of the battle. However, although Diodorus seems well informed, he tends to be casual about giving proper explanations. His simplified account is not always satisfactory.
As a conclusion I must say that I do not consider the contradictions between the accounts of Xenophon and Diodorus as important. I would rather view the pro-Spartan Xenophon and the well-informed Diodorus as two sides of the same coin. It is indeed difficult to harmonize the two accounts, but it is irresponsible to concentrate on either the one or the other.