Hermocrătes in Harpers Dictionary of Classical Antiquities
（Ἑρμοκράτης). One of the Syracusan generals, when the Athenians attacked Syracuse, B.C. 414. He was banished by the Syracusans (410 B.C.), and having endeavoured to effect his restoration by force of arms and with the aid of the Persian satrap Pharnabazus, was slain in 407. See Peloponnesian War.
Hermocrates in Wikipedia
Hermocrates (Ancient Greek: Ἑρμοκράτης) was a general of Syracuse during the Athenians' Sicilian Expedition.
The first historical reference to Hermocrates is at the congress of Gela in 424 BC, where he gave a speech demanding the Sicilian Greeks to stop their quarrelling.  In 415 BC he proposed a coalition that would even include non-Sicilian cities (as well as non-Greek cities such as Carthage) in an alliance against Athens. 
He was elected as one of Syracuse's three strategoi, but was dismissed from this position after a short period of time because of his lack of success in battle. Later he was one of the most important advisors to the Spartan general Gylippus, and thus contributed to the victory over Athens during its siege of Syracuse .
In 412 BC he held the position of admiral during the battle of Cyzicus. In this battle, the Spartans and their allies were badly defeated by the Athenians and, as a result, Hermocrates was banned "in absentia". He did not return to Sicily until 408 BC. He died in a street fight after a failed coup in Syracuse in 407 BC.
Besides Thucydides, Hermocrates is mentioned by Xenophon, Plutarch and Polyaenus. Hermocrates is one of the persons appearing in Plato's late dialogues Timaeus and Critias. Plato originally might have planned a third dialogue named Hermocrates, but never wrote it. "Since the dialogue that was to bear his name was never written, we can only guess why Plato chose him. It is curious to reflect that, while Critias is to recount how the prehistoric Athens of nine thousand years ago had repelled the invasion from Atlantis and saved the Mediterranean peoples from slavery, Hermocrates would be remembered by the Athenians as the man who had repulsed their own greatest effort at imperialist expansion."