Forty-six nations, under thirty Persian generals, were assembled for the invasion of Greece. Over and above them were six chief marshals, five of whom were sons of the royal house. Among the infantry generals were princes of the royal blood, while Otanes, father of Xerxes’ queen Amestris, commanded the crack Persian Guards. The latter was not responsible to any marshal but took his orders directly from the king himself. ‘Why, O God,’ a countryman is reputed to have asked Xerxes, ‘have you taken upon you the form of a Persian man, changing your name to Xerxes, in order to lead the whole world to conquer and devastate Greece? You could have destroyed Greece without all that trouble.’
The crossing of the whole army by the bridges took about a week and Xerxes, who passed over with his royal bodyguard behind the sacred horses and chariot of his god, was now able to see from the European side of the Bosporus the full magic of this display of imperial might. Herodotus says that the men ‘crossed under the lash’, but this seems improbable. It is merely another instance of his painting a portrait of an oriental tyrant whose reluctant soldiers - unlike the Greeks - had to be forced into action. That the lash was applied to the pack animals is more than likely, for otherwise, if we accept the figure of something like 75,000 beasts, ranging from horses and mules to camels, there would have been an inevitable congestion on the bridges.
There was in any case a very good reason for the army to press on into the alien territory of Europe as fast as possible - water. The Persians with their excellent organisation had set up food-dumps and supply organisations throughout Asia Minor and the northern part of Greece, which already came under their control, but they certainly could not organise the streams, rivers and other sources of water-supply. Herodotus asks the question: ‘What water did not fail them except for that of the great rivers?’ On the salient question of the water-supply of the invasion army no authorities can equal Maurice, with his practical military experience as well as his personal knowledge of all the terrain covered by it in the long march. To paraphrase his conclusions after the forces had left Asia Minor -limited quantities of water could have been obtained by boring ‘but this was beyond their resources’. At the point where the columns crossed, although there was water at Maidos near the bridges this was not on their route, so throughout this stage the army would have had to carry its own water with it. Except for occasional springs and wells, it seems that the troops would have had to take four days’ supply with them in water-skins. It is possible that, along with the careful preparations of food depots, water-troughs had been erected for the animals in open ground around Gallipoli and at the northern end of the marsh midway between Melas and Aenos, which could have been kept filled by regular convoys from the Melas itself. The allowance for the troops would have worked out at about two quarts per day, ‘not an over-generous allowance for men marching in hot weather, whose food is dry grain’. Taking the estimate of the grand army’s numbers as 210,000 this would have amounted to 420,000 gallons of water. Presuming that much of this was carried by the camel corps, something like 15,000 camels would have been required (a good camel being capable of carrying 300 lb of water). It is the essential matter of water-supply which disproves the Greek tradition of the army being composed of three million men.
It was not until the whole force assembled at Doriscus near the large River Hebrus that they could be ensured of a really adequate supply. It is very probable that, as Herodotus describes, the army was marshalled here to be regrouped in preparation for their further advance. There was also a food depot at this point, and the animals would have found ample grazing-land along the banks of the river. Doriscus was an ideal place for the pause before the advance. There was, furthermore, a convenient fort, which had been founded by Darius, to serve as a general headquarters.
While the Persians prepared themselves for their assault on northern Greece, the threatened Greeks, at this last stage before the invasion of their homeland, were still in disarray. Having failed to secure the naval assistance from Gelon of Syracuse, with the abstention of the Cretans from any involvement, and with doubts existing as to whether Corcyra would send a squadron to the defence of the Greek mainland, the navy party under Themistocles was at a considerable disadvantage. It seemed clear from reports on the strength of the Persian navy that, even after the new shipbuilding programme, the Athenians and their allies would still be heavily outnumbered. There was considerable difference of opinion among the high command at Corinth, the Peloponnesians arguing that the best solution was a land-defence line to be drawn across the Isthmus. This, of course, could hardly appeal to Themistocles, or indeed any Athenian, for the suggestion implied that, if the worst came to the worst, all of northern Greece including Athens itself would be abandoned. He took refuge in an additional answer that the Delphic oracle had given to the Athenian delegates, after they had returned with the first dark prophecy that Athens was doomed and that her citizens ‘should flee to the ends of the earth5. (It is possible that he himself had some hand in ensuring the second more favourable, even if ambiguous, response.) This said that ‘all-seeing Zeus5 had listened to Athens5 prayer and that, despite a dire outlook, ‘the wooden wall alone shall not fall5. It went on to say that ‘divine Salamis would bring death to the sons of women after the corn is scattered or the harvest gathered in5.
Although the Delphic oracle took its usual care to make doubleended pronouncements (for instance, which nation’s women5s sons would die?), the mention of Salamis and of the wooden wall are quite specific. Pessimists took it all as a further warning of defeat, while others maintained that the wooden wall must mean the palisades of the Acropolis. The policy of Themistocles, however, had long been centred around Salamis. He saw the island as not only the place to which the government and army of Athens must withdraw if their city was captured, but also the area in which his new navy might best take on the Persian fleet in constricted waters, where the greater numbers of the enemy might well prove of no advantage but even a hindrance. It was up to him to convince the people, in the great debate that followed the second Delphic pronouncement, that his interpretation was the correct one. It is evidence of the powers and skill of this remarkable man that, despite his many enemies’ among the conservatives, despite the fact that his argument was a somewhat thin one, he somehow managed to win the day. His oratory was Churchillian as he pointed out that it was freedom which mattered above all. Cities could be rebuilt, but they were nothing in themselves. The essence of the state lay in its citizens. Themistocles appealed to the people over the heads of his opponents, and the people responded. His war-policy was overwhelmingly approved.
Troezen in the Peloponnese, which was reputedly the birthplace of the legendary King Theseus of Athens, was chosen as the place to which the women and children of Athens should be evacuated. The people of this comparatively insignificant city-state responded magnificently to this renewal of the ancient blood-tie. The old people together with household goods were to go to Salamis, while the treasurers and priestesses were to remain on the Acropolis (this for the sake of public morale). General mobilisation was proclaimed, the fleet was to be manned, and all men under fifty were expected to serve. The salient aspect of policy was that, when the triremes had been manned and furnished for war, one hundred of them were to proceed to meet the enemy at Artemisium off Euboea, while the other hundred were to cruise off Salamis and Attica. The point that must be remembered was that this whole operation, as conceived by Themistocles and approved by the Assembly, applied to the Athenians only. What the reactions of the Peloponnesian allies would be was an unknown factor. They might think very differently.
Themistocles now had the hard task of persuading the Peloponnesians against their ‘defence of the Isthmus’ policy. The Spartans, the Corinthians, and the inhabitants of Athens’ old-time enemy, Aegina, had to be made to realise that a forward defence of Greece was essential. It is not difficult with hindsight to see that a strategy which rested upon a defence-line across the Isthmus would certainly have failed. All the Aegean islands opposite the coast had either medised or in any case could easily be rendered ineffective by the Persian fleet. Nothing would have been easier with the weight of sea- and land-power to isolate the Peloponnese and then invade it. The Isthmus of Corinth defence-line would have proved in those days as easy to turn as that of Maginot in this century. A combination of Greek military skill with naval power, if most judiciously used, might just turn the scales against the Persians. The unlikelihood of success if one operated without the other had to be made clear. (Events were to do so in any case.) The shadow of Marathon, somewhat naturally, haunted all discussion. If the Greek hoplites had triumphed before on land, why should the same not happen again ? The answer should have been plain to all but the most conservative-minded. The expedition of Xerxes, on its vast scale, was designed to conquer Greece and all the Grecian West. First Greece, then the Ionian islands, then Sicily, and then the rich colonies in Italy - this was the intended progression of conquest.
Part of Themistocles’ strategy was inevitably dictated by the very natural Athenian suspicion that the Spartans might let them down, might rely on the defence of the Isthmus, might (for whatever given reason) procrastinate and turn up late - as they had done at Marathon. If the worst came to the worst and northern Greece was overrun, the Spartans might come to the conclusion that they could stay secure in the Peloponnese. They and the other allies had to be convinced that, on this occasion, it was all or nothing for every state which had declared to hold their ground against the might of the invader. For the first time in their history the Greeks had to learn to co-operate with one another. In only one respect did the Athenians have an advantage over the Spartans. If Attica fell and Athens was overrun, they would - even if worsted in a sea-battle - still have some ships left. The survivors could ‘do a Dunkirk’ and (after collecting women and children from Troezen), they could abandon Greece, sail south and then west across the Ionian Sea, and plant a new colony in Sicily or Italy. The Spartans, with their small fleet, were condemned to fight on the land - with no escape.
The agreed strategy of the Congress at Corinth had originally been for the Greeks to fight as far forward in Greece as possible. In the spring of 480, before Xerxes had crossed into Europe, they had acted on an appeal from Thessaly and sent a force of 10,000 hoplites to hold the ‘Mount Olympus Line’ at the coastal pass of Tempe. The idea of holding a line as far to the north as possible was sensible enough in itself, but the pass at Tempe could easily be turned. Themistocles himself had commanded the Athenian contingent and a Spartan named Euainetos the Lacedaemonian. It is significant that the latter was not a member of the royal family, and therefore that the Spartan contingent was not a major one - or one of the kings would have gone at its head as was the custom.
The Athenians must have provided the main body of the force. It had become obvious from early on that the chosen position was impossible to hold. Not only was it bypassed by two routes to the west of Olympus, but the local tribes, far from being co-operative, had already determined on a Persian victory. Agents of the Great King had been active in the area for some time, offering inducements to the northern Greeks not to put up any resistance. Quite apart from that, it was well enough known that the Aleuadae were pro-Persian, while Alexander of Macedon was in fact a vassal of Xerxes.
The latter, a smooth charmer, and ostensibly attached to the Greek cause, had a brother-in-law who was a Persian general (somewhat difficult to explain away) and had no intention of being involved in what he clearly saw as a coming victory for the Persians. However, he was trusted by the Greeks (possibly because he had once run in the Olympics and nearly gained a crown) and they went to him as a reliable source of information. So he was - up to a point - for naturally he knew the northern area far better than the Athenians or the Spartans did. He demonstrated the grave defects of the Tempe pass as a holding-place, and advised them to pull back while there was still time. The Spartan Euainetos was convinced, and Themistocles must have felt relieved. The loss of 10,000 hoplites, as well as about the same amount of lightly armed men who accompanied them, would have been an intolerable blow at the very start of the campaign.
Although he was in favour of an action, even if only a delaying one, as far north of Attica as possible, Themistocles must always have held to his original conception of a fleet engagement at a point carefully chosen to the Greek advantage. The Greek force accordingly had withdrawn, sometime towards the end of May, and marched south. Both the hoplites and their accompanying soldiers were no doubt pleased to be moving back nearer to their homes. Greeks at that time rarely engaged in battles outside their local known territory. The inhospitable and treacherous northern mountain area (full of semi-barbarians and Greeks who had ‘sold out’ to the enemy) could never have induced in them the instinctive patriotism of Marathon.