On the March: The Terracotta Army comes to London

Not since Tutankhamun's mask dazzled the nation more than 30 years ago has the British Museum played host to such a breathtaking display of timeless antiquity. As China's Terracotta Army arrives, Dan Snow traces its extraordinary history – and Tom Lubbock gives his verdict on the exhibition of the year

In the spring of 1974, two sweating labourers hacked at the soil in a remote spot of Shaanxi province, China. The land was parched, and new wells needed to be sunk. As they dug with the most basic tools, they noticed that gradually the light-brown soil was getting darker. By the time they were five metres below ground level, the soil was almost red. Suddenly a shovelful of earth uncovered a sculpted terracotta face with neatly styled hair and eyes that looked up, imperturbably.

In the spring of 1974, two sweating labourers hacked at the soil in a remote spot of Shaanxi province, China. The land was parched, and new wells needed to be sunk. As they dug with the most basic tools, they noticed that gradually the light-brown soil was getting darker. By the time they were five metres below ground level, the soil was almost red. Suddenly a shovelful of earth uncovered a sculpted terracotta face with neatly styled hair and eyes that looked up, imperturbably.

The labourers carried on digging. Soon it became clear that they had discovered something unique and incredible. The strange figure was not alone. It was just the tiniest tip of a mighty iceberg: one of dozens, then hundreds, then (as we now know) thousands of life-size figures buried beneath the dusty soil. In the weeks, months and years that followed, archaeologists flocked to the site to dig, brush and dust their way through what had turned out to be an enormous army of terracotta warriors. It was perhaps the greatest historical discovery of the 20th century.

Now, a group of those very warriors has arrived in London. On Thursday, we will witness the opening of the British Museum's most important exhibition for 30 years. The First Emperor: China's Terracotta Army will electrify the British public as surely as Tutankhamun's golden mask did in the 1970s. It is part of British Museum director Neil MacGregor's ambitious "China strategy", in which he hopes to forge a cultural alliance with the coming superpower of the East, and place Chinese studies at the heart of the British consciousness, where he and many modern academics believe it wholeheartedly belongs.

The exhibition is the result of years of painstaking diplomacy by curator Jane Portal. She has negotiated a visit by about 20 terracotta figures and other supporting objects, which represents the biggest ever overseas loan by the Terracotta Army Museum in Xi'an, and the finest collection of Qin dynasty artefacts ever shown in Britain.

Portal's success will enable the British public to gain an insight into one of the most influential and powerful men who ever lived. Many of the world's greatest archaeological treasures are connected with fairly marginal patrons who become household names thanks to what they left behind (Tutankhamun was a boy pharaoh of little importance; were it not for his tomb, only the most dedicated scholars would have heard of him). But what makes the Terracotta Army so exciting is that it was created to stand guard for all eternity over the tomb of one of history's greatest leaders – a man who forged a mighty empire from a set of disparate warring states, an empire that survived his death, thrived and still endures to this day.

This man called himself Qin Shihuangdi (pronounced Chin Shur Hwang Dee), and he was the First August Emperor of Qin. He lived from 260BC to 210BC. In later centuries, barbarians beyond the borders of his empire would hear of this vast new realm and come to call it China. He was the founder of one of the largest and most important nations in human history.

One mile to the west of the spot where the Terracotta Army was discovered is the giant tomb mound of Qin Shihuangdi. It is an 80m-tall earth pyramid, which stands on top of a burial chamber containing his tomb. The people of China always knew that it was the tomb mound of the First Emperor but they had no idea of its real scale.

After the discovery of the warriors, a series of further digs took place. In all, 600 pits were discovered over an area 56km square. There are, without a doubt, many more to come. The tomb mound is only the centre-piece of a giant necropolis, which, in the words of Portal, "consists of an underground governmental system, which as we dig we realise is larger than we ever thought." The enormous Terracotta Army was simply created to be the gate-keeper of one of the biggest tombs ever.

Forget 1066, 1492 and 1945. The most important date in human history is 221BC. That year, Zheng, the King of Qin, one of several adjoining and belligerent states, emerged victorious from a war that for over two centuries had raged through much of the area now known as China. In quick succession he annexed competing states such as Chu and the once mighty Zhao. In 221BC, the last one, Qi, surrendered without a fight. Zheng became Qin Shihuangdi, and worked to bind his conquests into one nation.

He worked ruthlessly to crush regional variation. He aimed at nothing less than universal rule. He carved proclamations on mountains across eastern China, announcing that, "the bright virtue of the August Emperor aligns and orders the whole universe." The impressive bureaucracy that had fed, armed and marshalled his armies now set about winning the peace. Several hundred thousand forced labourers built thousands of miles of roads and canals. He constructed what is possibly the most magnificent palace ever built, the Ebang Palace. He joined a series of protective walls together into a vast defensive system that formed the first Great Wall of China.

Qin Shihuangdi divided his empire into 36 parts and chose officials to govern them. Highly unusually, these men were appointed on the basis of merit alone. Punishments were carefully proscribed for every kind of misdemeanour; they were unremittingly harsh. The Emperor was no bleeding-heart liberal – Confucian ideas on the essential nobility of the human spirit had no place in his ordered world. Only strict discipline would ensure unity in his fledgling and diverse empire.

His state interfered in its citizens' lives in a way that feels more 20th century than third century BC, and is strangely analogous with modern-day China. Qin Shihuangdi unified the Chinese script, suppressing regional variations. He made certain that from now on the people of his new empire would all speak the same language. He insisted that carts had axles of the same length so that ruts would be regular on the country's roads. Where he found variety, he standardised.

It is this legacy, measured over millennia, that makes Qin Shihuangdi virtually unique. Not only did his armies conquer an empire to rival that of Alexander, Napoleon or the Caesars, but he consolidated those conquests and forged a state that still endures. Many of his administrative innovations remained until the fall of the last emperor in 1911, and some are still discernable even today. Today, China is poised to become a superpower. Its far-flung provinces and different ethnic groups are brought together by a powerful cultural and linguistic centrifugal force that owes much to Qin Shihuangdi's reign. He is, quite simply, one of the most influential men ever to have lived.

The ambition of his necropolis suggests that Qin Shihuangdi was aware of – and almost obsessed by – his legacy. He had good reason to be worried about the afterlife: he had annihilated the armies of six opposing states. Chances were that they would be out for revenge.

Nothing on such a scale had ever been attempted before. Some 700,000 labourers were mobilised. His tomb complex contained a vast underground palace so that he could continue to rule for eternity. His court, his bureaucracy, his army – in fact, an entire universe – was all buried with him. Terracotta bureaucrats, acrobats and stable boys were interred, but also real people: his childless concubines, officials and labourers. Humans, spirits and demons would all interact in a supernatural world impenetrable to the modern mind.

While archaeology has been constantly shedding light on some of the pits surrounding the central mound for more than 30 years, no work has been allowed on the mound itself. The only description of what might be inside the tomb comes from a single history, written 100 years after the first emperor's death: the Shiji, the records of the "grand historian" Sima Qian.

According to the scribe, "craftsmen were ordered to set up crossbows and arrows, rigged so that they would immediately shoot down anyone attempting to break in. Mercury was used to fashion the hundred rivers, the Yellow River and the Yangtze, and the seas in such a way that they flowed."

Finding the terracotta warriors, which were not even mentioned by Sima Qian, forced historians to accept that the almost mythical stories about the grandeur of Qin Shihuangdi and his tomb may have had a good deal of truth to them. In June 2007, the Chinese announced that they have used ground-penetrating radars to confirm that there is, indeed, a 30m-high chamber inside the mound.

Although the tomb mound remains untouched, excavations are continuing nearby. In its shadow is one of the most recent pits discovered: the Stone Armour Pit. It is thought to be more than 13,600m square, but so far they have excavated only 1 per cent of it. The enormity of the challenge posed by just this one pit is daunting to Wu Yongqi, the director of the site. Bizarrely, his greatest fear is that "there will be more finds." His overstretched resources are inadequate as it is. He "dreams of a day when technology sheds light on all that's buried" without having to dig it all up by hand.

The Terracotta Army itself is a perfect reproduction of Qin Shihuangdi's all-conquering forces. There are light infantry, cavalrymen, archers, heavy infantry and senior officers to command them. They were lined up in underground tunnels, the roof supported by wooden beams; they were never intended to be seen by the living.

Every one of them was produced on an assembly line and then finished by hand. Each one is therefore subtly different. Hairstyles are different: some wear their hair in plaits, others have it swept up into a top knot, some wear soft caps. The shape and size of their noses, eyes and beards change. Some look to be central Asian, others have flatter noses and Mongol features. The commanding officers are noticeably more rotund, their barrel chests exuding authority.

All the soldiers were armed with real weapons. To make them even more lifelike, they were painted in lacquer. The faces were pink, the armour bound by red ribbons, and a garish collection of greens, yellows and bright blues made up the rest. The British Museum has included a replica in their exhibition painted in the original colouring, a dazzling piece that only emphasises how intriguing it was that the figures were designed to be lined up in the pitch black.

The army might have proved their might in the spirit world, but in the all-too-human world that Qin Shihuangdi left behind they turned out to be as much use as, well, clay soldiers. Crisis followed Qin Shihuangdi's death. His son was not up to the job of ruling his empire and usurpers fought between themselves. After nearly 10 years of civil war, Liu Bang emerged victorious. He assumed the title of emperor in 202BC and founded the Han dynasty, which ruled for more than 400 years and consolidated Qin Shihuangdi's achievements. The First Emperor had boasted that his descendents would rule for 10,000 generations. That proved optimistic, but his empire lasted until the 1911 revolution, and his legacy continues today.

Whether or not to excavate Qin Shihuangdi's tomb is now the burning question. Wu Yongqi is dead against it, but there is a sense that some of his younger colleagues are straining at the leash.

Portal thinks that on balance Wu Yongqi is right: "They are right to be cautious. It is the most important archaeological site in China. Techniques of conservation are improving and they should wait. In the 1950s the Ming tombs were excavated and Chinese archaeologists have regrets about some of the things that were done." Either way, the tomb complex of Qin Shihuangdi will remain the most exciting archaeological site on the planet for decades to come.

In China, Qin Shihuangdi is enjoying a resurgence. The nation is rejecting the old ideological view of him as a violent despot and embracing him as a founder. His stock rises as Chinese confidence grows. He was even the subject of Zhang Yimou's film Hero in 2002. The Chinese do not doubt his enduring relevance; we in the West would be wise to follow their example. The First Emperor exhibition is a useful starting point if we are to fill the woeful gaps in our knowledge about the world's oldest continuous civilization.

'How can we be Chinese without them?'

While the 2008 Olympics have come to symbolise China's pride and sense of achievement about its recent rise, the Terracotta Warriors remain a potent emblem of national honour. And if the pottery army's longevity is anything to go by, they'll be around a lot longer than the heroes of next summer's games.

The discovery of the warriors back in 1974 put the ancient former capital on the map again. Now, two million people throng to Xi'an, capital of Shaanxi province, to see the army every year.

Museum head Wu Yongqi, who looks after the warriors of Qin Shihuangdi and their stone horses, has expressed the modest hope that the exhibition " will help the British people learn something about China's military and art 2,200 years ago."

The Chinese are fiercely proud of the soldiers and the fact they are travelling to Britain, China's old colonial foe, is a source of quiet satisfaction. To get a feel for just how proud the Chinese really are of the Terracotta Army, you only have to surf the web and read the tourist brochures, which never miss an opportunity to trumpet the warriors as " the most significant archeological excavations of the 20th century".

"The grandeur and superb workmanship fully demonstrate the great talent and vision of the Chinese nation... These artistic treasures of the Qin Dynasty are without doubt, one of the world's great wonders," enthuses one tourism site.

A trawl through Beijing's top academies reflects the same pride among their students. "The Terracotta Warriors reflect the gorgeous ancient culture of China. The Army is a symbol of great royal power in China in ancient times, and it also reflects the idea of life and death, just like the mummies in Egypt," says Zhang Hong of Peking University, 25. Sun Yunfei, a 23-year-old student, says that the soldiers show the power of ancient China and the wisdom of the people back then.

Office worker Shen Si is even more patriotic: "How can we be Chinese without them? This is our nation's past, a mirror of great imperial power, different from other relics such as the Summer Palace and the Temple of Heaven."

Clifford Coonan

Tom Lubbock: 'One man's legacy: an astonishing work of conceptual art'

You tend to overpack. Because packing is an act of imagination. Anything that might turn out to be a need in an emergency, is a need. And so the bags fill up, and eventually the whole house has to go in. But even a very important person, with a highly active imagination, going on the biggest journey of their life, might feel that a cargo of 8,000 life-size clay figures – you know, just in case – was stretching it.

One of the perks of the Christian religion is that it requires you to take nothing at all with you on your final voyage. Everything, fire or bliss, will be laid on at the other end. The dead rise naked from the grave. And while Christian countries have wasted their resources in many ways, they have at least not spent them on filling the tombs of their kings with huge quantities of afterlife luggage.

The Terracotta Army of the Emperor Qin Shihuangdi is the most spectacular archaeological find of modern times. In 1974, a farmer drilling a well in Shaanxi province – it's always a farmer – made the first accidental breakthrough into their underground bunkers.

The figures have travelled abroad before. Six were shown at Selfridges in 1981. But never so many, and it's not all that many – just a dozen warriors, plus four bureaucrats and athletes, plus horses, and some bronze birds – are going on show this week in the high-domed and atmospherically darkened rotunda of the "Reading Room".

Emperor Qin is the notional subject of the show, and there's a good deal of fast-history to be consumed – text projections, artefacts in glass boxes, reconstruction films – but it's the human and animal figures in clay and bronze that are obviously the main attractions in this show. And even with the mighty army reduced to a small search party, everything one learns about it is likely to instil awe. There is the amazing fact that this highly accomplished realism, which looks like the culmination of a long tradition, had no precedent in Chinese art and seems to have been invented for the occasion (it then vanished afterwards).

What you get in the British Museum is not numbers, of course. It is proximity, a chance to see the figures much closer up than is possible in Shaanxi; to stand before them as they stand before you, to look at them face-to-2,000-year-old-face, and... Well, I know, I know. Everything points towards the word mesmerising. But I'm afraid I couldn't summon it.

The figures in their pieced body armour are fascinating bits of workmanship, and their faces have undeniable character – but charisma? Not quite. You sometimes get a magical effect with statues, when the figure is depicted in the act of tensely standing still, and it's as if the stillness of the statue itself was an act of will that might at any moment break. But these are inert sculptures – stiff and stuffed, rather than tense. The horses and birds are wonderfully modelled, though, as is the fat acrobat.

Still, it is odd to treat these figures as single free-standing sculptures, when they were made to stand in dense, thronged ranks. And as the eye dwells on their baked-clay surfaces, it is all too easy to put out of mind the fact that – like ancient Greek statues – the warriors were originally painted in gaudy, realistic colours, and equipped with real bronze weapons, more like effigies than sober works of art. Now that the paint has mostly fallen off, we're too liable to love them inauthentically, for their plain, honest, earthiness.

But what am I talking about? The authentic state of these figures? That's a hopeless quest. Because their authentic state was, quite simply, total invisibility. These parades of brightly painted figures stood, in their low-ceilinged bunkers, sealed from view. That's how they were meant to be "exhibited", in pitch darkness. What might look, in the light of day, like an ancestor of installation art was in reality more like an ancestor of conceptual art, a work along the lines of Marcel Duchamp's With Hidden Noise.

Having discovered them and dug them up, naturally no one's going to roof them all in again. But as you gaze at the warriors, in London or in China, you can't but be thrown back by the knowledge that this elaborate and monumental work of visual theatre was never intended to be seen by anyone.

Or rather, which may make things slightly less mysterious, never intended to be seen by anyone living. The warriors were recruited for the parallel universe of the dead. That explains the attention of their workmanship. You could compare them to carved figures high up on European cathedrals, quite out of sight, but given the same attention to detail as those near the ground. We humans aren't the only audience around.

There is that little rhyme by Longfellow: "In the elder days of Art,/ Builders wrought with greatest care/ Each minute and unseen part;/ For the gods see everywhere." The warriors are not temple fixtures. They have a more practical purpose – to be an army in the afterlife. But the magic only works if you get them right.

And they speak for us all, do they not? The Emperor Qin, with his super-human burial complex, may seem like an extravagant megalomaniac, but he was hardly unique. He was only uniquely well-placed to give free rein to the basic human tendency not to know when to stop. The desire to be master of the universe and the desire for eternal life are only the lunatic conclusions of our normal wishes.

You just wanted to – oh, you know – get a bit more in shape and feel a bit more in control of things? But where would you draw the line, if the line wasn't drawn for you? And if you thought that building a massive necropolis, and taking an army with you, would guarantee you immortal domination of the cosmos – and if you could – well, wouldn't you? I think so. Don't forget your toothbrush.

The First Emperor: China's Terracotta Army (020-7323 8000; www.britishmuseum. co.uk), 13 September to 6 April

Dan Snow's programme, 'China's Terracotta Army', will be transmitted on 15 September on BBC2 at 8pm