Who is Lysander from Tides of War: A Novel of Alcibiades and the Peloponnesian War and what is their importance?

Lysander is a brilliant Spartan general and politician. He isn't as honorable as Alcibiades, and is known to have a cruel streak. Over the course of the novel, it is this trait (cruelty) that enables him to defeat Athens. Lysander, unfortunately, is more concerned with political advancement and glory than the people he protects. Under his leadership, Sparta is reduced to a shadow of its former self.