As the association of the Classical period's opening chronological boundary with clashes against Persian forces and of its close with the military expeditions of Alexander reveals, the Classical period of Greek history was an age often marked by turbulence and war. The Golden Age of Athens was no exception, and one bloody conflict after another raged in mainland Greece during the fifth century, beginning with war against the great kingdom of Persia, whose heartland lay in what is today southern Iran. The kingdom of Persia had by around 500 expanded far enough westward that the Greeks were becoming aware of its enormous might, but neither the Persians nor the Greeks, especially those on the mainland, yet knew much about each other. Their mutual ignorance opened the door to explosive misunderstandings and a deadly war. When the Greeks allied against the Persians managed by 479 to defeat their more numerous foe and expel its invading army from the Greek mainland, the way was opened to the full blossoming of the Golden Age. After their success in the war with the Persians, however, the two major powers in mainland Greece— Sparta and Athens , who had cooperated in fighting the Persians—gradually became more and more hostile to each other in the course of the fifth century. Eventually, their mutual suspicions and hostilities erupted into open warfare of Greek against Greek, culminating in the drawn-out and destructive Peloponesian War (431-404) between Athens and Sparta and their allies. This catastrophic struggle lasted for twenty-seven bitter years. Athens' defeat in this war brought an end to the Athenian Golden Age.

The sources of the strife ² between these two major powers of the Greek mainland are significant for an understanding of the history of the Athenian Golden Age because that greatest era of Athens' prosperity and cultural achievement came to an end as a result of the terrible defeat inflicted on Athens by Sparta and its allies in the Peloponnesian War. Sparta, dominated politically by a conservative oligarchy ³ that was always suspicious of change, had already become concerned by the end of the sixth century by the development of greater democracy at Athens under the leadership of Cleisthenes after 507. The Spartan leaders feared that the increasing democratization of Athenian government under the reforms of Cleisthenes ⁴ would lead Athens to contest Spartan predominance in Greece. After seeing the military power, epecially the navy ⁵ , that Athens marshalled against the Persian army, the Spartan leaders increasingly saw Athens as more than just a theoretical threat to their state's dominance. The majority of men at Athens reciprocated this feeling of suspicion and feared the Spartan army, Greece's most formidable infantry force, as a threat to their international ambitions and security. The allies of Athens and Sparta also contributed signficantly to the friction between the two powers by complaining to their respective leaders about real and imagined grievances against the other leading state.