the 17th of the Eurypontid line (beginning with Procles), succeeded his father Archidamus, B. C. 427, and reigned a little more than 28 years.
In the summer of B. C. 426, he led an army of Peloponnesians and their allies as far as the isthmus, with the intention of invading Attica; but they were deterred from advancing farther by a succession of earthquakes which happened when they had got so far. (Thuc. 3.89
In the spring of the following year he led an army into Attica, but quitted it fifteen days after he had entered it. (Thuc. 4.2
.) In B. C. 419, the Argives, at the instigation of Alciblades, attacked Epidaurus; and Agis with the whole force of Lacedaemon set out at the same time and marched to the frontier city, Leuctra. No one, Thucydides tells us, knew the purpose of this expedition.
It was probably to make a diversion in favour of Epidaurus. (Thirlwall, vol. iii. p. 342.) At Leuctra the aspect of the sacrifices deterred him from proceeding.
He therefore led his troops back, and sent round notice to the allies to be ready for an expedition at the end of the sacred month of the Carnean festival; and when the Argives repeated their attack on Epidaurus, the Spartans again marched to the frontier town, Caryae, and again turned back, professedly on account of the aspect of the victims.
In the middle of the following summer (B. C. 418) the Epidaurians being still hard pressed by the Argives, the Laccdaemonians with their whole force and some allies, under the command of Agis, invaded Argolis.
By a skilful manoeuvre he succeeded in intercepting the Argives, and posted his army advantageously between them and the city.
But just as the battle was about to begin, Thrasyllus, one of the Argive generals, and Alciphron came to Agis and prevailed on him to conclude a truce for four months. Agis, without disclosing his motives, drew off his army. On his return he was severely censured for having thus thrown away the opportunity of reducing Argos, especially as the Argives had seized the opportunity afforded by his return and taken Orchomenos.
It was proposed to pull down his house, and inflict on him a fine of 100,000 drachmae.
But on his earnest entreaty they contented themselves with appointing a council of war, consisting of 10 Spartans, without whom he was not to lead an army out of the city. (Thuc. 5.54
, &c.) Shortly afterwards they received intelligence from Tegea, that, if not promptly succoured, the party favourable to Sparta in that city would be compelled to give way. The Spartans immediately sent their whole force under the command of Agis.
He restored tranquillity at Tegea, and then marched to Mantincia.
By turning the waters so as to flood the lands of Mantineia, he succeeded in drawing the army of the Mantineans and Athenians down to the level ground.
A battle ensued, in which the Spartans were victorious.
This was one of the most important battles ever fought between Grecian states. (Thuc. 5.71
.) In B. C. 417, when news reached Sparta of the counter-revolution at Argos, in which the oligarchical and Spartan faction was overthrown, an army was sent there under Agis.
He was unable to restore the defeated party, but he destroyed the long walls which the Argives had begun to carry down to the sea, and took Hysiae. (Thuc. 5.83
In the spring of B. C. 413, Agis entered Attica with a Peloponnesian army, and fortified Deceleia, a steep eminence about 15 miles northeast of Athens (Thuc. 7.19
); and in the winter of the same year, after the news of the disastrous fate of the Sicilian expedition had reached Greece, he marched northwards to levy contributions on the allies of Sparta, for the purpose of constructing a fleet. While at Deceleia he acted in a great measure independently of the Spartan government, and received embassies as well from the disaffected allies of the Athenians, as from the Boeotians and other allies of Sparta. (Thuc. 8.3
He seems to have remained at Deceleia till the end of the Peloponnesian war. In 411, during the administration of the Four Hundred, he made an unsuccessful attempt on Athens itself. (Thuc. 8.71
.) In B. C. 401, the command of the war against Elis was entrusted to Agis, who in the third year compelled the Eleans to sue for peace.
As he was returning from Delphi, whither he had gone to consecrate a tenth of the spoil, he fell sick at Heraea in Arcadia, and died in the course of a few days after he reached Sparta. (Xen. Hell. 3.2.21
He left a son, Leotychides, who however was excluded from the throne, as there was sone suspicion with regard to his legitimacy. While Alcibiades was at Sparta he made Agis his implacable enemy. Later writers (Justin, 5.2
; Plut. Alc. 23
) assign as a reason, that the latter suspected him of having dishonoured his queen Timaea.
It was probably at the suggestion of Agis, that orders were sent out to Astyochus to put him to death. Alcibiades however received timely notice, (according to some accounts from Timaea herself) and kept out of the reach of the Spartans. (Thuc. 8.12
; Plut. Lys. 22