Sicily and Athens
The soil in and around Athens was very poor from an agricultural point of view. Grain and other crops would barely grow at all. The soil and in particular the grain that was produced on Sicily was of a great interest to Athens, and was being observed throughout the war with Sparta. Greek colonies founded on Sicily, the largest of which was Syracuse, remained neutral throughout the war.
Segesta, which was an ally of Syracuse, was having internal problems with the Sicilian city of Segesta. Athens was invited to help resolve this dispute by Segesta.
Alcibiades, who was a second cousin of Pericles, managed to convince Athens that they should send a small fleet of vessles there. They would go with the cause of helping Segesta, but in fact they would go to assault Syracuse. This was because Syracuse was the daughter-city of Corinth.
This mission was a disaster for Athens from the offset. The leadership of Alcibiades, Nicias and Lamachos was not a very pleasant one. Malmachos was killed and the health of Nicias suffered badly. Alcibiades was ordered back to Athens to answer charges of blasphemy. However, instead of returning to Athens as directed, he fled to Sparta.
This led to dismay from Athens and surprise for Sparta. Successful in becoming a counselor for one of the Kings, Alcibiades was able to convince Sparta to come out of its isolation. Alcibiades then convinced them that it would be in Sparta’s interests to send men to the aid of Syracuse.
Gylippus, who was one of the most powerful and respected generals in Sparta, went with a group of men. The result was the defeat of Athens in Sicily, where they suffered heavy losses in both ships and men. However what followed was even more disastrous for Athens and eventually led to the second Peloponesse war.