After the conclusion of the peace of Nicias (421 B.C.) he marched against the Argives in defence of Epidaurus, and after skilful manoeuvring surrounded the Argive army, and seemed to have victory within his grasp when he unaccountably concluded a four months' truce and withdrew his forces.
This represents the Argive Dorians as having come by sea (apparently from the Maliac Gulf, the nearest seashore to Parnassian Doris), accompanied by survivors of the Dryopes (former inhabitants of that Doris), whose traces in south Euboea (Styra and Carystus), in Cythnus, and at Eion (Halieis), Hermione and Asine in Argolis, were held to indicate their probable route.
The American explorations of the Argive Heraeum, concluded in 1895, also failed to prove that site to have been important in the prehistoric time, though, as was to be expected from its neighbourhood to Mycenae itself, there were traces of occupation in the later Aegean periods.
In addition to researches at Sicyon, Plataea, Eretria and elsewhere, it has undertaken two works of capital importance - the excavation of the Argive Heraeum and of ancient Corinth.
But the peace of Antalcidas dissolved this connexion, and barred Argive pretensions to control all Argolis.
The Argive Heraeum was the most important centre of Hera and Juno worship in the ancient world; it always remained the chief sanctuary of the Argive district, and was in all probability the earliest site of civilized life in the country inhabited by the Argive people.
Opposite them stood another semicircular basis which carried the statues of the Argive kings, whose names are cut on the pedestal in archaic characters, reading from right to left.
Another important aspect of Demeter was that of a divinity of the under-world; as such she is XBovia at Sparta and especially at Hermione in Argolis, where she had a celebrated temple, said to have been founded by Clymenus (one of the names of Hades-Pluto) and his sister Chthonia, the children of Phoroneus, an Argive hero.
These statues bear the same relation to the sculptor Polyclitus which the Parthenon marbles hold to Pheidias; and the excavations have thus yielded most important material for the illustration of the Argive art of Polyclitus in the 5th century B.C.
Hellanicus a generation later repeats this blunder, and identifies this Argive and Arcadian Pelasgus with the Thessalian Pelasgus of Hecataeus.