The Persians are coming! The ancient Persians, that is, of the Achaemenid Empire (550-330BC), in honour of whom a major exhibition curated by John Curtis opens at the British Museum next week. One of the exhibition's prize objects, to be seen outside Iraq and Iran for the first time, is the so-called Cyrus Cylinder discovered at Babylon in 1879. Curiously, that was the year after the dramatic date of one of Tom Holland's earlier books, the historical thriller The Bonehunter.

Cyrus is Cyrus II the Great, the Empire's founder, and the text of the Cylinder has been hailed a touch enthusiastically - not to mention anachronistically - as an early declaration of human rights. Actually, it concerns the repatriation of religious statues and human deportees, recalling that it was the same Cyrus who earned the title "Lord's Anointed" from Deutero-Isaiah for restoring the exiled Jews from Babylon to Judaea.

It was as a human rights document that the UN had the text translated in 1971. That was the supposed 2500th anniversary of Cyrus's death - an event commemorated with unseemly grandiosity by another Shah an Shah (King of Kings). How were the mighty to be fallen! Within a decade, the Peacock throne of Mohammed Reza Pahlavi was no more. A revolution that still casts its long shadow over the world, and not least the West, had swept it away.

It is Tom Holland's plausible contention, in this brilliant sequel to his award-winning Rubicon, that Achaemenid Persia was the first truly world empire and that, had Cyrus's grandson Xerxes succeeded in his attempted conquest of the Greek mainland in 480, there would not have been much if any "West" for that shadow to fall over.

This is incendiary stuff, and the igneous metaphor that blazes from the cover has a deeply serious antique relevance. Cyrus erected fire-holders at his original capital of Pasargadae; Xerxes trailed news of his would-be exploits from Europe to Asia by a series of fire-beacons. And the Empire's second founder, Xerxes's father Darius, yielded to none in his absolute devotion to the Lord Ahura Mazda: god of light and life, implacable enemy of the Lie, whose worship - founded by the prophet Zoroaster (Zarathustra) - centred on rituals involving fire.

Tom Holland's non-fiction but - inevitably - slightly fictionalised account of what the Greeks called "the Median things" (they were incapable of distinguishing the Medes from their southern Iranian cousins and vanquishers) is the first in English addressed to a general readership for more than 30 years. In it, Holland crosses his own Rubicon, from Roman history to Greek, but not only Greek by any means. One of the book's many attractions is the care lavished on trying to get under the skin of the Persians, especially those of the imperial court and wielding the highest military commands.

Indeed, as the title is surely meant to suggest, he - like the professional ancient historian George Cawkwell in The Greek Wars (2004) - wants us to see the wars from the Persian just as much as the Greek side. Special attention is paid to the Persians' religion, one that lives on in the modern world from Mumbai to Vancouver in the observances of the Parsis (whose name betrays their ethnic origin).

Holland emphasises the causal, motive force of royal Persian opposition to the Lie. Xerxes's invasion of Greece should not for obvious reasons be called a crusade. But there was about it something of the same spirit that animated the anathema on all daivas (demons) that Xerxes delivered in a famous trilingual text - Old Persian, Elamite and Babylonian - found at his chief ceremonial capital. This magnificent site the Greeks later called Persepolis; the name that has stuck to this day, thanks not least to Alexander the Great's symbolically definitive destruction of it in 330. The big trouble for Xerxes was that his monotheist Mazdean zeal was met with an equal and opposite force from his polytheistic Greek enemies.

The key religious aspect of the culture-shock was brought out beautifully by the Wars' great pioneering historian, the Asiatic Greek intellectual Herodotus of Halicarnassus (modern Bodrum). One of the leitmotifs of his historia (enquiry, research) - to which, for all its imperfections, Holland like the rest of us is ultimately in hock - was the theme of hubris.

Xerxes overstepped the limits - of power, of geography, of humanity - and paid the price. He had the waters of the Hellespont whipped, as if the Hellespont - for the Greeks a divine force - was but one more of his millions of human bandaka (slave) subjects. For that sacrilegious confusion of categories and tyrannical transgressiveness, Xerxes paid the appropriate tisis (divinely authorised restitution).

Another case of royal whipping, this time of his own troops, also caught Herodotus's eye, and it has resonated to this day. This occurred at the first land battle of Xerxes's campaign, fought at the "Hot Gates" of Thermopylae. John Stuart Mill declared the battle of Marathon, won ten years earlier against Darius, to be "even as an event in English history... more important than the battle of Hastings". The same could, and should, be said of Thermopylae, at which the self-sacrificing Spartan king Leonidas and his 300 champions won immortal fame.

Holland does Thermopylae full justice within the broader scope of his account, which also treats expansively the other major conflicts at Artemisium, Plataea and Mycale. Throughout, the reader's attention is caught by sparkling insight and no less sparkling writing. At Thermopylae there were horridly visible "viscera spilled across the ground"; Regent Pausanias of Sparta, the victor of Plataea, was a "notorious enthusiast for barbarian chic"; the Syrian Gates functioned as "a tourniquet ever ready to be applied, in case of emergency, to the flow of the Royal Road". The narrative is studded and always enhanced with such luminous and arresting phraseology.

Nor does Holland fail to rise to the seriousness and vastness of his East-West theme. If you read nothing else, do read the Preface, which succeeds in its aim of building a bridge between the worlds of academic and general readers. Indeed, one of the most astonishing aspects of the author's achievement here, as in Rubicon, is that this is a book written by someone trained neither in the (Greek and Latin) classics nor even in history, let alone Oriental Studies.

If Persian Fire does not win the Samuel Johnson Prize, there is no justice in this world. The Lie will have triumphed, again. "Look to the end," a character in Herodotus warns. So a final word to the wise (judges): yet another Greek divinity, Nemesis, always lies in wait to punish hubris. And it is the inexorable goddess Nemesis with whom Tom Holland aptly ends his grippingly, acutely relevant logos (tale).

Paul Cartledge is professor of Greek history at Cambridge University. His 'Thermopylae: turning-point in world history' will be published by Macmillan in 2006, and the paperback of 'Alexander the Great: the hunt for a new past' by Pan this October