The Athenian Temple on Delos is probably executed around 425 BCE by Callicrates (to whom architectural historians, on stylistic grounds, attribute the work.)

Sparta in 425 BCE resumes its strategy of annual invasion.

Samothrace joins the Delian League around 425 BCE.

Demosthenes, whose credit with the Assembly must now be excellent, is in 425 authorized to use the Athenian fleet for operations around the Peloponnese.

He occupies and fortifies the remote promontory of Pylos in Messenia and, while the rest of the flotilla sails on to Sicily, remains with five ships at the harbor of the peninsula at Pylos.

Here, he manages to resist attacks by the Spartans, …

…who, in foolish reaction, occupy Sphacteria, the long island to the south of Pylos, but this force of four hundred and twenty men, about half of them full Spartan citizens, are cut off and besieged after their ships are driven off by the returning Athenian fleet.

This gives the Athenians a potentially valuable bargaining chip.

Sparta sues for peace without reference to its allies, but Cleon persuades Athens to turn the offer down.

Cleon makes steep demands, including (in effect) the cession of Megara, showing that he—like Nicias in 427 and Demosthenes (and Hippocrates in 424)—grasps the strategic importance of Megara.

By declining the diplomatic solution, Cleon finds himself committed to a military one.

He succeeds dramatically, capturing one hundred and twenty full Spartans and …

…taking them back to Athens.

This operation, achieved partly with the use of light-armed troops, ensures that there will be no invasion of Attica in 424.

Athens is free to establish a base on …

…the island of Cythera south of Laconia.

Segesta’s inhabitants begin construction of a Doric temple on the summits of two adjacent hills in 425 BCE. (Never enclosed, the temple may have been intended as an open-air sanctuary.)

Artaxerxes, who has retired to Persepolis, dies peacefully in late 424 and is buried at Naqsh-e Rustam.

Xerxes II inherits the Persian throne from his father and is murdered a few weeks later by his brother Secydianus (or Sogdianus).

Sogdianus is in turn murdered by his paternal half-brother Ochus, satrap of Hyrcania, the son of Artaxerxes by a Babylonian concubine, who now assumes the kingship as Darius II.

Also known as Nothus (Bastard), Darius is dominated by eunuchs and by his half sister and wife, the cruel and ambitious Parysatis.

Perdiccas helps the Spartan Brasidas in 424 BCE to take Amphipolis from the Athenians, one of her most important colonies, mainly for its ready access to timber for her fleets.

This is a severe blow to Athens, and will tie them to Macedonian timber for years to come, which strengthens Macedonia’s bargaining power considerably.

In return for this, the Spartans help Perdiccas secure his borders, by leading an assault on King Arrhabaeus of Lyncestis, with the promise of support from the Illyrians.

However, the Illyrians switch sides and attack Perdiccas and his Spartan allies.

The poorly trained Macedonian troops flee, and so the Spartans also retreat and attack the Macedonian baggage train in anger.

This sours relations between Macedonia and the Peloponnese for years to come, and pushes Perdiccas closer to Athens, with whom he will ally Macedon in 423.