Hostilities between Athens and Aegina resume at the beginning of the Peloponnesian War, and the Athenians deport all of Aegina's population and replace them with Athenian settlers in 430.

Euripides, in the initial phase of the war, writes a patriotic play, “The Children of Heracles.”

Pericles himself comes down with the disease after leading a ravaging expedition against Epidaurus—probably to bar Corinth's eastern sea-lanes completely—and other Peloponnesian places and defending himself against his critics.

No obvious success counterbalances the discomforts of war, and Pericles is deposed from office and fined.

The second year of the Peloponnesian War, 430 BCE, begins with another invasion of Attica by the Spartan army, again led by Archidamus II.

The middle-class army suffers in morale, and the living conditions of the lower classes, though they are allowed activity in the fleet, deteriorate in the overcrowded city.

The severe overcrowding of Athens in the second summer of the Peoponnesian war has an unforeseeable consequence in a plague that, although it cannot be securely identified with any known disease, carries off a quarter of the Athenian population, including one-third of the fourteen thousand hoplites and cavalry.

Herodotus has traveled widely: he has gone to Egypt at least as far south as Elephantine (Aswan); he has also visited Libya, Syria, Babylonia, Susa in Elam, Lydia, and Phrygia.

Journeying up the Hellespont to Byzantium, thence Thrace and Macedonia, he had traveled northward to beyond the Danube and to Scythia eastward along the northern shores of the Black Sea as far as the Don River and some way inland.

Herodotus names as Getae (Getians) the Thracian people living in the Carpathian-Danube region.

Intimate knowledge of some events in the first years of the Peloponnesian War (VI,91; VII,133,233; IX,73) indicate that he might have returned to Athens, in which case it is possible that he died there during an outbreak of the plague.

Possibly he died in Macedonia instead after obtaining the patronage of the court there or else he died back in Thurium.

Either way, there is nothing in the Histories that can be dated with any certainty later than 430 and it is generally assumed that he died not long afterwards, possibly before his sixtieth year.

Potidaea has surrendered, and a cleruchy is installed here too, a further Corinthian setback, in 430 BCE.

Phormio, the Athenian general who had headed the siege of Potidaea, is sent to block the entrance to the Gulf of Corinth with twenty ships in 430 BCE.

Few other Etruscan cities have responded to the call for assistance from Veii, whose King Tolumnius dies in battle with a Roman general around 430.

The Middle East: 429–418 BCE

Stability, Revolts, and Imperial Administration

Under Artaxerxes I and subsequently Darius II (Ochus), the Persian Empire experiences a period marked by internal stability interspersed with localized rebellions, especially in peripheral satrapies. Artaxerxes I dies peacefully in 424 BCE after a notably long reign, succeeded by his son, Darius II, whose rule immediately faces internal unrest and challenges to imperial authority.

Darius II works diligently to reestablish control over revolting territories, including regions such as Asia Minor, where ambitious satraps attempt to assert greater autonomy from central Persian oversight. His reign is characterized by persistent efforts to re-centralize power, maintain imperial cohesion, and stabilize frontier provinces.

Despite these ongoing administrative and military challenges, the Persian Empire remains intact, functioning through its established satrapal system, with the court at Susa continuing as a cultural and political hub. The empire's core provinces enjoy relative prosperity, benefiting from the enduring Persian administrative structure, robust trade networks, and cultural integration fostered over previous generations.