Of the two great Greek historians, Thucydides is traditionally the favourite of strategists; Herodotus of travellers and adventurers.  But read against the backdrop of the Russian invasion of Ukraine, Herodotus’ Histories, which tells the story of Greek resistance to the Persian invasion has a fresh, and strategic, salience. An Asian invasion force coming out of the East with massively superior forces against a smaller and vulnerable European state is defeated and repulsed through courage and will. Herodotus anatomises why the Persians lost. For all those hoping for a similar outcome for European Ukraine against the aggressor from the East those lessons are worth rehearsing.

Numbers are no guarantee of victory: it’s will not mass that counts

In Book 7 of the Histories Herodotus reconstructs a conversation between Ahasuerus and his advisors whom he summons in a form of Persian ‘national security council’, to tell them of his invasion plans. Led by Mardonius, his self-seeking cousin, the advisors sycophantically support Xerxes making swaggering reference to the superiority of Persian numbers and arms (‘What have we to fear? … When it comes to arms there is no one to match us’). But things go differently for Xerxes when Artabanus, his uncle, speaks. Exercising the license he enjoys as a senior royal Artabanus makes the important point that Xerxes should not underestimate his enemy. The Greeks are not like other opponents such as the Scythians. They are qualitatively different. They are determined, skilled, and courageous fighters. Secondly, he notes, there is no substitute for good planning and strategic patience of which he has seen neither (‘the offspring of haste is error’ he says). Moreover, Artabanus warns the meeting that numerical superiority is no guarantee of victory. He argues it is a form of excess abhorrent to the gods. Put in a more secular idiom, he is arguing that numerical superiority leads to overweening behaviour which could hand the advantage to a smaller force.

Herodotus is of course using the dialogue to reinforce his caricatures of the Greeks as valiant defenders of freedom and the Persians as bullying tyrants. But Artabanus is, here and elsewhere, a vehicle for more general truths about the nature of asymmetric warfare. Xerxes, however, is furious with Artabanus’ intervention and batters him with his rationale for the war: Persia is the subject of aggression; Persia must take the initiative against the Greeks not just in Attica but ‘the whole of Europe’ to eliminate the threat; taking counsel of their fears will just leave the Persians victim to further aggression; and besides, he throws in, the Peloponnese was once part of Asia. After he has spoken, Xerxes promptly closes the meeting. His rationale for war is already complete and he is not prepared to risk it being compromised by challenge. He has made an emotional commitment to invasion which over-rides any calculation of risk or strategic consequences. Xerxes is responding to a perceived slight, a perceived threat, and a deeply internalised sense of the power of Persia and its natural, as yet unreached, limits. Xerxes’ outburst serves the literary purpose of showing that invasions are, in their grandeur, a function of visions more often than strategic calculus.

But immediately after the meeting, Herodotus’ narrative takes a dramatic turn. Xerxes dismisses the security council but then falls to reflecting on Artabanus’ words and decides that perhaps an invasion is not such a good idea. Sleeping on this, he is troubled by a dream in which a mysterious figure taunts him with his decision not to invade. Xerxes shrugs off the dream and in the morning tells the council the invasion is off. But then the figure returns in a dream the following night with the same rebuke, and Xerxes is badly thrown. He believes this is a message from the gods he cannot ignore. But, just to be sure, he asks Artabanus to assume his duties, and clothes, for a day as the figure will, if a god, then surely wing his way to Artabanus. Sure enough, Artabanus is visited by the same figure with the same message tailored for him as Xerxes’ advisor. Xerxes then knows he must invade: it is divinely ordained. His emotional commitment to an invasion has thus been challenged but has emerged stronger. It is now locked in by divine sanction. Dreams and visions drive invasions.

The more territory is taken, the harder a land war gets

Years after the council meeting and the dream sagas, when Xerxes has conquered Egypt and the Greek campaign is underway, the Persian army pauses at Abydos ready to cross into Greece over the pontoon bridge across the Hellespont. Artabanus and Xerxes have another dramatised conversation in which Artabanus, at this eleventh hour, expresses again his concerns. He is very worried about two aspects of the campaign: land and sea. He worries that the Persian fleet will not find adequate ports, and that the land army will be weaker the further it advances into Greece. The latter point is an important observation about the nature of large-scale land war: the invader’s supply lines and vulnerability lengthen with each victory. Artabanus notes in addition the related traps of momentum and ambition: it is hard for an army, once it has started acquiring land, to know where to stop. Artabanus’ fear is that of the most basic threat to the Persian army: starvation as the army outruns its supply lines.

Artabanus is also concerned about the human geography of conquest. He notes that using conquered Greeks (the Ionians) to attack others (Attic Greeks) will be high risk. The Persians will be putting them in the invidious position of choosing to resist them or their fellow Greeks. Their loyalty cannot be relied on. Ethnic loyalties will be stronger than geographic ones, and the assumption, by extension, that conquered territory brings the benefit of manpower and resources is a false one. It is largely risk and cost.

Xerxes acknowledges Artabanus’ fears but he is already committed to the invasion. He dispatches him back to the imperial capital of Susa, convenes his security council to ensure they all have their hands dipped in the blood of invasion then gives the signal for the Persian horde to start crossing the Hellespont. The invasion is on.

Herodotus charts the course of the ensuing Second Persian War with colour and verve, his narrative arc climaxing in his immortalisation of the heroic defeat of the battle of Thermopylae, and again with the victory at sea off Salamis and the final defeat of the Persians in Ionia. He attributes the Greek victory not to their superior military skill, although he gives them more credit than the Persians did, but to their love of liberty and the strength of their determination not to live under an alien system where the rule of one man is paramount. Will in the end triumphed over mass. But not before great sacrifices had been made, alliances tested and betrayed, and Greek lives and property (including Athens itself) occupied and destroyed.

It is a story ultimately to give heart to the Ukrainians who have already shown their valour against numerical odds and their readiness to fight like the Spartans. As Xerxes is reminded by the exiled King of Sparta, Demaratus: ‘even if they are only a thousand, a thousand of them will fight.’

Of course the Russians know more than most about land wars having fought them in defence and offence throughout their history. But one lesson from Herodotus is hard to ignore. They are encapsulated in the final words of Artabanus to Xerxes before the fatal order to cross the Hellespont. They would have rung in the ears or Xerxes and should do so in the ears of Vladimir Putin: ‘The end is not obvious at the beginning.’