There can be no doubt that there was some hard bargaining, even threatening, at the various meetings which took place. The Spartan Ephors kept quibbling and fobbing the Athenians off with promises to let them have a decision on the following day, and so on. It was not until after the Athenian envoys had given up in disgust, and were on the point of leaving yet again, that the Ephors seem to have rethought the whole situation. One of the principal advocates of responding to the Athenian call and marching north was Chileus, an important citizen of Sparta’s neighbour, Tegea, who appears to have commanded considerable influence among the ruling class in that strange state. Having heard from the Ephors that the Athenians were again bringing up the threat of forming an alliance with the Persians under the conditions that Xerxes offered them, he pointed out the grim reality of the situation, saying: ‘As I see it, gentlemen, if the Athenians desert us and make an alliance with Persia, then, however strongly the Isthmus is fortified, the postern gates are wide open for the Persian invasion of the Peloponnese. So you had better listen to them before they change their minds and adopt a policy which will ruin Greece/ In this, of course, he was absolutely correct. Without the aid of the Athenian fleet the Isthmian wall would have become as redundant as did that of Maginot centuries later. It would merely be bypassed and the Athenians would land the Persian army wherever they wanted in its rear.
After prevaricating for so long, the Ephors now acted with haste. Almost overnight 5000 Spartiates, out of what was probably a total of 8000, were mobilised and on the march north. With them, according to Herodotus, went 35,000 Helots. These would have been lightly armed troops, but good fighters none the less, as they had already proved at Thermopylae. One reason for taking such a large number of Helots was possibly the fact that, with the bulk of the Spartiate army on its way out of the country, the Ephors did not want to risk any chance of a Helot uprising. In any case the Helots, too, could see that Persian victory would not improve their position but would turn them into total slaves under the Persians and their sympathisers. Pausanias was put in charge of the whole campaign, his cousin King Pheistarchus, the son of Leonidas, being only a boy. Pausanias was himself only in his twenties but he had great strength of character, as he was to prove, and had probably from the very start been one of those who advocated an active policy as against the more conservative Ephors.
The speed of the mobilisation and of the Spartan army’s march to the Isthmus was such that, even if the Argives ever had any intention of fulfilling their promise to Mardonius to stop any Spartan move to the north, the Spartans were already passing their frontier. It is difficult to believe, in any case, that, faced by such a weight of men, Argos would have dared to take any action. They did, however, send a runner with a message to warn the Persian commander that ‘the fighting force of Lacedaemon is on the march, and that the Argives have been powerless to stop it’. One can only presume that this young Argive bypassed the Isthmian line in a small boat before making his way to Mardonius. All the members of the Spartan league mobilised with almost similar swiftness and marched to join Pausanias at the Isthmus, only Mantinea and Elis were too slow in moving and missed the campaign that was to follow. Mardonius now knew there was no doubt that a large Peloponnesian force combined with the Athenians portended a battle which, even with his numerical superiority, was going to be a hard one. He knew how only 300 Spartiates with a few thousand behind them had held up the full weight of the Great King’s army at Thermopylae.
Athens and Attica must again be abandoned and he must fall back on Thebes, where the territory around the Asopus river would afford him the chance to deploy his cavalry in good measure. At the same time, as he knew from the Thebans who had already suggested that he make their city his base, he would have pro-Persian allies whose greatest desire was to see Athens permanently destroyed. Before he left the city he once again sacked as much of it as he could, even though the time-factor prevented his demolition teams from leaving the site as barren as he would have liked. Attica itself, however, was once again ravaged. Mardonius, like any intelligent general, had no intention of leaving food and fodder for an army that was clearly intending to advance against him, and not just hold a defensive position on the Isthmus. For the first time, perhaps, he must have felt more than a twinge of unease. He had failed to divide these two principal Greek states. He knew about the calibre of the Greeks, and in particular the Athenians, at sea; and he knew about the Spartans’ prowess on land. The beacons had signalled from island to island across the Aegean the second capture of Athens and of all the Attic land. He was a close blood relation of Xerxes, but that did not count too closely in an autocracy where the title ‘King of Kings’ literally meant what it said.
Mardonius had already begun to withdraw into Boeotia when he received a message that an advance guard of a thousand Spartans was in Megara. Thinking that he might at least eliminate this enemy body without much difficulty, he detached part of his army - probably a fairly large cavalry unit - and sent them down to the area. The report, as it turned out, was false and some of his men were cut off and killed by the Megarians. This abortive raid was, in fact, the farthest to the west that the Persians ever got in the whole of Xerxes’ campaign in Greece. What had started out as the invasion of western Europe was now turning into a retreat with only the possibility of a massive victory in a pitched battle to procure any chance of Xerxes’ achieving even a part of his original dream.
Withdrawing by way of Decelea, the easternmost pass over the Parnes range, possibly choosing this route because he feared that an advance guard of Spartans or Athenians might have reached one or other of the easier routes and be lying in ambush for his forces, Mardonius was met by local guides. The army stopped for a night at Tanagra and then made for a village called Scolus which lay in Theban territory. Herodotus relates that ‘in spite of the fact that the Thebans were on his side he cut down all the trees in the neighbourhood - not as an act of hostility to Thebes, but simply for his own military need, for he wished to construct a palisade to protect his troops and to have somewhere to retreat to in the event of the battle going against him’. The encampment on the north of the river-line of the Asopus also commanded the roads leading to Thebes itself. It possibly extended for about five miles. Mardonius thus could maintain his friendly contacts and communications behind him. The Thebans, now aware of the size of the force that was soon going to break into their territory, and of how far they were committed to the Persian cause, would probably have been quite willing for the Persians to cut down almost every tree in their area if it would serve to protect them from the wrath of Athens and Sparta. (Incidents such as this, combined with many later wars in Greece, together with the eternal demand for wood for shipbuilding, contributed to that deforestation of the land which has never over all the centuries been successfully reversed.) The area of Mardonius’ camp, as carefully calculated by Burn, would probably have accommodated an army of ‘60-70,000 men, of whom 10,000 might be cavalry’. In any case, even after the addition of several thousands of Boeotians and other Greek allies, it is unlikely that Mardonius had any great superiority in numbers over the allied army that was marching to meet him. There can be little doubt he had come to believe that the Athenians would come over to the Persian cause, and that the Peloponnesians, entrenched behind their Isthmian wall, would never join up and march in a united front against him. He had calculated that, in the seemingly eternal inter-state rivalry and hatred of the Greeks, he could ‘Divide and Conquer’. What he, and Xerxes and all the Persian high command, had failed to understand was that these two Greek states - however much they might basically dislike each other - were united against any subjection by an autocratic foreign tyrant.
Evidence of the mistrust felt between the Greek allies, even in this moment of their greatest need for co-operation, is to be found in the famous Oath of Plataea. This was probably administered after the junction of the Athenians under Aristeides, and Pausanias with the Spartiates and other Peloponnesians, at Eleusis. After all the threats and counter-threats that had passed between the principal partners it is not so surprising that something like a sacred oath binding all parties to be true to one another in the hour of battle was considered necessary. There are various versions of the Oath of Plataea, but it is difficult not to sense an Athenian hand behind its construction. The version quoted here is a fourth-century transcription dedicated in Acharnae by one Dion, priest of Ares, the war-god, and of Athena, in her role of war-goddess. The reason one suspects an Athenian behind the Oath’s composition is that most of the military requirements itemised would have been familiar, and indeed automatic responses, to a Spartiate after ‘his first term at school’.
I will fight to the death, and I will not count my life more precious than freedom. I will not leave my officer, the commander of my Regiment or Company, either alive or dead. I will not withdraw unless my commanders lead me back, and I will do whatsoever the Generals order. I will bury the dead of those who have fought as my allies, on the field, and will not leave one of them unburied. After defeating the barbarians in battle, I will tithe the city of the Thebans; and I will never destroy Athens or Sparta or Plataea or any of the cities which have fought as our allies, nor will I consent to their being starved, nor cut off from running water, whether we be friends or at war.
And if I keep well the oath, as it is written, may my city have good health; but if not, may it have sickness; and may my land give increase; but if not, may it be barren; and may the women bring forth children like their fathers; but if not, monsters; and may the cattle bring forth after their kind, but if not, monsters.
The whole Greek army now moved out from Eleusis on the road to Thebes. The Athenians had hoped that Mardonius would give battle early, but it was now clear that he intended to make his stand farther north and force the allies to march up to meet him. It was now late July and the farther he could make heavily armoured men sweat over a dusty, burned-out plain the more chance there was of them arriving in an exhausted condition. After putting the plain behind them they had to climb up the slopes of Cithaeron and emerge at the top of the Eleutherae Pass. Ahead of them now lay the steep descent towards the Asopus, on whose northern bank lay Mardonius with his army entrenched behind his palisade. It was indeed good generalship on his part to have forced the allies to come to meet him, while his own men rested, rather than engage them earlier in the plain of Eleusis. The sight might have daunted the Greeks: the harsh way down, the shine of the river, the impressive stockade, the Persian forces deployed, the city of Thebes behind them, and then the great Boeotian plain, with Helicon and Parnassus shining in the far distance.
The Athenians are said earlier to have obtained an oracle from Delphi promising them success if they fought ‘in their own land, in the plain of the Eleusinian goddesses Demeter and the Maiden’. When they had been forced to advance into Plataean territory they must have felt some dismay, but the Plataean leader Arimnestus, supposedly inspired in a dream sent by Zeus, solved this problem by persuading his fellow Plataeans to take up their boundary stones on the side facing Attica, thus making a gift of all this Plataean land to Athens. (There is no record as to whether they ever got it back again.) The matter of achieving victory ‘in the plain of the Eleusinian goddesses’ was another matter altogether. This was solved by the discovery of an old temple of Demeter of Eleusis near Hysiae, at the foot of the Pantanassa ridge. It was an area which would be very favourable for the Greeks to take up their battle stations since the Persians would have little chance of deploying their cavalry. Mardonius watched and waited as the Greeks came down and took up their position in the foothills, hoping by a show of inertia to lure them out into the plain. When they showed that they had no intention of obliging him,
Mardonius sent his cavalry to attack them in force, under the command of the distinguished Persian officer Masistius … who rode a Nisaean horse with a bridle of gold and other splendid trappings. The cavalry advanced to the attack in successive squadrons, and at each assault inflicted heavy losses on the Greeks, taunting them and calling them women. It so happened that the point in the Greek line which was most open and vulnerable to a cavalry charge was held by the Megarians, who found themselves hard pressed by the repeated attacks.
It is possible that the division from Megara was astride the road to Thebes and there were no more than 3000 of them. Pausanias, receiving a call for help, very sensibly despatched not his own heavily armoured hoplites, who would have been of little use in the situation, but the Athenian regiment of archers. As was to be shown in many later wars over the centuries horsemen were particularly vulnerable to nimble men armed with the bow and arrow. Herodotus makes the imputation that Pausanias called for volunteers to back up the men from Megara and that only the Athenians responded. (This is clearly part of his later pro-Athenian bias.) He continues: ‘For some time the battle continued, until, during the successive attacks of the Persian squadrons, Masistius’ horse, which was in advance of the rest, was shot in the flank… .’ The horse reared up and Masistius fell to the ground where he lay as helpless as many a medieval knight, for he was wearing under a scarlet tunic a corselet of golden scales. The Athenians rushed upon him, but, despite futile thrusts at his armoured body, it was not until a soldier pierced him through the eye-slit of his helmet that the Persian cavalry leader was killed. The other members of his squadron had not seen him fall, for his horse was hit just at the moment when they were wheeling back before making a further charge. ‘It was only when they drew rein again that they missed him - for there was no one to give the commands.’ The whole of the Persian cavalry force at once lined up and charged all together, determined upon recovering Masistius’ body. It was now the turn of the Athenians to suffer heavy losses and to be forced back. At this point Pausanias and the main body of hoplites came to their support and, confronted by the armoured wall and the bristling hedge of spears, the Persians called off the attack and withdrew. They failed to recover the body of their leader - something that in those days was always considered a grave disgrace, and caused a corresponding loss of morale. Uncertain as to what to do, the cavalry reported back to Mardonius.