After this, in March, 418, without further warning, the Spartans equipped a large force of all kinds under King Agis against Argos, and marched upon its territory. The Argives met them. There was no time to get help from Athens. Some of the higher families in Argos, like the aristocracy in Athens, favoured Sparta and an oligarchic government. By their influence a truce for four months was concluded with King Agis. Then the Athenians, seeing there was something weak in Argos, sent Alkibiades as ambassador there, to help the democratic party to keep up against their Spartan enemies without and their traitorous aristocracy within the city walls. They also sent a force of horse and foot to aid them, under Laches and Nikostratos. The people of Argos were at first afraid to break the truce which had been made against their will with Sparta. It required all the eloquence of Alkibiades in their Assembly to prevent them sending back this help from Athens.
He spoke to them of what, in times gone by, they had endured at Sparta’s hands; how Sparta was still as great an enemy to them as ever; how ‘two years ago they had made that solemn pact with Athens; how well the Athenians had kept it on their side; how it had been ratified at the ninetieth of the Olympic celebrations.’ There were shouts of applause as he thus modestly referred to the scene of his late victory. Warmed by this token of their favour, he concluded: ‘Oh men of Argos, while we are here to go with you to death or victory, while we are sworn never to leave you till you have overcome this treacherous foe, will you go back from your promises, and leave a name to after-times like that of Sparta, as breakers of your word and faith, and of a treaty of alliance ratified before the whole of Greece, and at the very dwelling-place of Zeus?’
He had almost as great a success in the Assembly at Argos as he had when he first proposed the treaty with them at Athens. The people decreed with acclamation that the war with Sparta should go on; the truce was at an end. They at once proceeded to lay siege to Orchomenos, in Arkadia, to the north of Mantineia. They took it, and then marched on towards the oligarchic Tegea, a firm ally of Sparta. The Spartans, too, marched towards Tegea, and took up their position near the temple of Herakles, and began plundering the Mantineian country. The Argives and Athenians, together with the Arkadians from Mantineia, met them in the low country near Mantineia. The Argive force took up a strong position on the steep side of Mount Artemision, where it would be difficult to attack them, and whence they might with advantage descend upon the Spartans in the plain below.
King Agis saw that to assail the allies upon this vantage-ground would be to court defeat, and yet he must do something. There were ugly rumours about him in the camp, as well as at Sparta. He was threatened with a prosecution. It was said against him that the truce he had made was in itself an act of treason, that he had the Argives in his power then, and had spared them for some purpose of his own, and had, by letting them go, enabled them to get help from Athens.
However, for all that they might say of him, he was firm, and led his army away till he came to a stream on the boundaries of Tegea and Mantineia, about which the inhabitants of those places were continually quarrelling. On to whichever territory it might be turned, it would do considerable damage. Agis began to divert this stream on to the land of Mantineia, thinking that this would bring the Mantineians, and perhaps the whole Argive force, down from their place of vantage to stop the flow of water.
Upon the other side there were murmurs too. ‘Are we to stay here like pigeons in a rock for ever? See how the Spartans leave their ground! Will you let them escape us now as you did before? It seems to us there must be treason amongst our generals. Are they not of the aristocrats, and oligarchs in secret? For aught we know they may be in correspondence with the oligarchs of Sparta.’ The Argive generals were weak and frightened, and knew not how to act. They had no doubt as to the tactics of the Spartan king, and yet they dare not keep their army waiting in its present mood. If Alkibiades had but been there, his firm command would soon have made itself respected, as it will be seen in this story to have often done. He could do anything with the Argive people, who had greater faith in him than in their own generals. But he was away in Argos acting as ambassador, and had no authority to interfere in the military operations, or the future course of Greek affairs in this portion of Arkadia might have gone differently for Athens and for Sparta.
So on that night in June the Argive force, with their allies, descended from their strong position, whence they could defy the enemy, and bivouacked upon the plain, ready next day to meet or to pursue him.
The enemy soon returned in marching order, and took up their former post by the temple of Herakles, determined, if their strategy had not succeeded, to try to take the Argive position by assault. The strategy, they found, had succeeded but too well, and, as they descended the Tegean defile, they discovered their opponents, drawn up in full array, in the open plain before them. To change from column into line was with the well-drilled Spartans the work only of minutes, and their adroitness called forth admiration from Alkibiades, who, unable to get up to them, was watching from a distance.
He saw the Mantineians posted on the right, with a body of Argives and Arkadians in the centre, while on the left were the Athenian foot and his own comrades of the cavalry. He saw the Argives advance in haste and fury, and the Spartans slowly to the music of their pipers, which kept them in step together and in perfect order. He saw the Mantineians charge the left wing of the Spartans grandly, and break their line, and follow them, as they retreated, to their waggons. He saw with anguish the Spartan king dealing out destruction on the Athenians and the others of the Argive force, and about to overwhelm them, when, to his astonishment and delight, Agis drew off his men and hastened to assist his left wing, which was being harassed by the Mantineians as it retreated.
Now was the time for the Athenian horsemen to charge the Spartans in the rear; now his own cavalry might outflank the king; but there they stood motionless, demoralized. Both their leaders, Laches—his old friend Laches—and the other general, were slain. There was no one to encourage them, no one to lead them, none who was capable of rising to the great occasion, and they slunk unworthily away.