Not since Hitler hatched plans for an invasion of England has the arrival of an army been so anticipated in our country. The First Emperor, which opens this week at the British Museum, is our chance to catch up with the most momentous archaeological discovery of the 20th century. Finally, visitors will come face to face with the near-legendary warriors of China’s terracotta army. Little wonder that temperatures are running high.

This show is being compared to the landmark Tutankhamun blockbuster, which back in the Seventies racked up an attendance of more than 1.7 million. Advance ticket sales are already breaking box-office records. Soon the queues will be running round the block. But will it be worth it? Must you join the crush? The answer – though it may not be apparent at first glance – must emphatically be yes.

The outcome of years of diplomacy and planning, this exhibition represents the biggest display of terracotta warriors yet to be lent outside China. But when you tot them all up – including the charioteer’s stocky clay horses – only 20 figures are actually included. That’s hardly an army. It’s not even a platoon. This show doesn’t pretend to recapture the giddying awe of an on-site encounter with even that fraction (only 1,000 of about 8,000 figures) of the army that has already been excavated. It can hardly recreate the overwhelming wonder that the visitor to China must surely feel as he first comes face to face with phalanx after phalanx marching out of eternity: a marvellous, mysterious, inscrutable mass.

We know very little about the artisans who made them, starting sometime after 228BC, except that they worked in teams supervised by one of around 87 foremen, identified by seals they stamped on some of the figures as a form of quality control.

When compared with Tutankhamun’s glittering treasures, the emperor’s companions in the realm of immortals might appear at first glance a rather shabby little posse. As patched and repaired as old teddy bears, they have lost all but a few faded traces of the brightly coloured pigments that once gave them dazzling presence. The archer’s bow has disintegrated. The musician’s zither has rotted. The acrobat’s spinning plate has broken and the strongman’s weights have dropped. Exhibition designers and curators have to work hard to create a sense of spectacle. But they succeed brilliantly. The museum’s great Round Reading Room has been temporarily adapted into an atmospheric show space, which, with its soaring dome, does not really need such additions as the fairylight screen of stars to indicate that we are stepping into the lands of sublime dream. Massive photographs, cinematic reenactments, computerised replicas and stone rubbings come together with archaeological objects and a few reconstructions to dramatise a story with impressive concision and clarity.

It is quite a story that this show has to tell. We in the West may not be familiar with Qin Shihuangdi, the first Emperor of China. But this megalomaniac scion of a tribe of horse-traders, who first came to his throne when he was barely in his teens and who, from this vantage point, subdued the warring peoples of vast Eastern expanses, was clearly one of the most extraordinary men who ever lived. It was he who turned China into a single powerful political entity and, from 221BC, ruled as the first emperor of the nation to which he gave his name (Qin is pronounced Chin).

Through displays of archaeological artefacts this show introduces us to the breathtaking scale and sophistication of his achievements. It looks at the martial culture that brought him his power, laying out the weapons and tactics of his formidable war machine. It explores his astounding civil innovations: his introduction of a common currency, a standardised system of weights and measures, a single script and even a regulation axle width so that carts could cross the entire nation using the same ruts.

Each object is presented so that it can be seen from all sides – which is more than can be said for the First Emperor’s story, which is given a pronouncedly diplomatic slant. Of course, it’s unsurprising that a man who boasted that his “might shook the four extremities” would have been an ambitious and hardheaded military figure. But the ruthless barbarity of this ruler, with whom Mao Zedong identified, is barely acknowledged in this show. Thousands suffered and died under his brutal tyranny. His opponents were tortured and massacred. Scholars were, at best, quickly slaughtered; at worst buried alive. And in a maniacal quest to attain his own immortality, the lives of unnamed masses were uncaringly sacrificed.

This destruction is not the focus. Instead, as we step into the domain of his astonishing necropolis, in which he set out to make his own replica of the entire universe, we are encouraged to focus on the creative spirit of this astonishing project. A model reconstructs the production-line assembly of the clay figures, feet first, the hands fitted separately from a varied selection, the individually sculpted heads fitted last. Enthusiasts are offered a chance to catch up with on-site archaeological developments.

But all this information is concisely presented. You have to read the catalogue if you want any detail. What actually confronts the visitor is a pretty pared-down display that takes as its primary focus the terracotta figures. These are what you will stand and stare at. Look carefully and you will be spellbound.

Anyone can recognise the sentiment. From a distance a personality is a mere component of a vast military machine. But then the individual steps forward. At first you distinguish him by his outward accoutrements. You pick out the different headdresses, haircuts, styles of armour or shoe of the various divisions and ranks. There is a wonderful attention to detail in these figures, from the size of the armour links (the smaller the link, the more comfortable to wear and the more labour-intensive to make, and therefore the higher rank the man who wears it) to the hairstyles of the horses (long plaits for the cavalry, bunched-up for charioteers). But the longer you look the more subtle the distinctions grow. Compare the bulky general to the lissom acrobat; the bureaucrat’s slouch to the taut military stance. The figures may have begun as production-line models but each is adapted: big clay buttocks are slapped onto a portly officer; the great paunch of the strongman hangs over his belt.

But it is only as they come into emotional close-up, as you confront them face to face, that you start to feel the full force of this extraordinary achievement. Figures that start out as the remote denizens of some alien dream turn into people that we recognise and know. You can’t help suspecting that the heads were sculpted by accomplished craftsman who possibly borrowed techniques from the West. China was certainly open to influences entering along its ancient Steppe Road, as a gold dragon belt-hook with faïence eyes suggests.

You can see the spread of cultures which this empire must have incorporated in faces that range from delicate Turkic features to broad Mongolian heads. But there is something more universal even than that in this show. It lies in the expressions of the faces, in the shapes of the eyes and the set of the lips. You can pick each one out like the character of a person that you know. You can feel a profound sense of relation. In the end, it is not the achievements of an emperor that this show celebrates, but the lives of these individuals, upon whom his empire was founded.

This exhibition may not offer the sheer visual glitter of Tutankhamun. But it has a vast emotional spread. Here is an army that invades the imagination. You must see this show.

The long march of the terracotta warriors

246BC Ying Zheng becomes King of Qin state and begins work on his tomb.

221BC Ying Zheng, now known as Qin Shihuangdi, unifies the country we know as China and declares himself the First Emperor.

210BC Qin Shihuangdi dies of an illness on tour. The terracotta army is buried near his tomb.

c 208BC General Xiang Yu raids and burns the tomb, damaging all the clay figures except one.

1974 The tomb is accidentally unearthed by local farmers drilling to create a well.

The First Emperor: China’s Terracotta Army is at the British Museum, WC1 (020-7323 8000), from Thursday.

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