The Peloponnesian War is an adventure that shook and in many ways sealed the history of Ancient Greece. Military events succeed political decisions and vice versa, forming a complex historical framework. In this ongoing effort for dominance between Athens and Sparta, both sides try to influence the psychology of their opponents, as well as that of their friendly audience. In this work, an attempt is made to view Thucydides' texts from a perspective different from the simple recording of historical events. In this light, we understand that psychological operations, under whatever name or characteristic they were given at the time, played a significant role in the development of the Peloponnesian War. We observe the protagonists of the civil conflict employing all the known means at the time in order to influence the target audience and achieve their goals. Thucydides' work, possibly without the great historian intending it, preserves valuable historical information about the conduct of psychological operations until today. And thus, we are led to a new and original interpretation of Thucydides' work.