It's one of the world's greatest engineering wonders the Great Wall of China They say it can even be seen from space. It is a military masterpiece that has witnessed hundreds of battles, Yet it still holds many mysteries. British writer and historiam William Lindsay has lived in China for 20 years. Exploring the Great Wall has become his lifetime obsession. Lindsay has spent thousands of days on the Wall has walked thousands of kilometers along it. How long is the Great Wall really? How many years did it take to build? And why was it built at all? It is only a short trip from Beijing to one of China's most popular attractions. Millions of tourists come here every year to see the stone dragon. The Great Wall of China. Most of the people walking on the Great Wall, here today will go home and say, "I have been to the Great Wall of China" but the Great Wall is not a place it ranges across the sub-continental expanse of North China and along its course. many of the locations seldom visited and some are virtually unknown. In 1987, Lindsay fulfilled his childhood dream. He walked on the Chinese Wall 2,700 kilometers. Only a few pictures remain from this adventure because his films were repeatedly confiscated. Foreigners were barred from many parts of China. Those times have long changed. China has opened up to the world and an adventurer has turned into a schollar. Lindsay now seeks out traces of the Great Wall of China. right across the country. Twenty three years after his first trip he sets off again. Doing the same, exploring 23 years later is really testament of the immensity of what we call the Great Wall of China. In the last two-and-a-half decades I explored the Wall more 1,700 days, I have discovered it is the world's most famous building but the least-known. There is always something new to discover. There is no single Great Wall. There are lots of walls in northern China. built by different dynasties for more than 2,000 years. William Lindsay is taking us to one of the most remote places a 2,300 kilometers drive west of Beijing to the city of Dunhuang, into the Gobi Desert. I drove nearly there some 75 miles northwest of Dunhuang and that is a nice sunny day in the Gobi Desert, perfect conditions for exploring the Great Wall. In the shimmering heat the dark ribbon along the horizon at first looks like a mirage but these really are the remains of a wall. literally in the middle of nowhere. Well, one of the most precious parts of the Great Wall of China this is the Han wall built 2,100 years ago. I am not the first traffic to come here. This is the Silk Road. So, merchants would come from the deserts in Central Asia entering China at this point and then proceed east to the heartland of China. So, let us take a close look. Built over 2,000 years ago, this wall looks completely different to the familiar Great Wall near Beijing. It is not built of stone but this construction material has kept it strong for milennia, reed and gravel. But who was this wall meant to protect so far from civilization? The Han dynasty rulers wanted to open their empire to trade with the west. So they secured control of the eastern end of what became known as the Silk Road. The Han Chinese occupied the vital ashi??? corridor that runs along the Silk Road between the northern steppes and the Hymalayan foothills. It is a real border, not just between peoples but between lifestyle. The nomads of the steppe live in yurts, the traditional round tent. They live entirely from their livestock wandering over the steppe. They pitch their yurts wherever they find grazing land for their herds. After enduring long hard winters in the stepes these nomadic warriors ransacked China's northern provinces. Year after year they killed and ??? stealing food and metals everything their lifestyle prevented them producing. The Chinese regarded their Empire as the cradle of civilization. According to their Confucion philosophy it was the cultural centerof the world. Appeasing the barbarians along the border by trading was out of the question. War was too expensive. So, the Han Emperor decided to build a wall. How many people were involved in rhe construction of the Han wall? No one knows for sure. but reliable sources quote the calculations presented to the Emperor. If one soldier can build three paces of the wall in one month, then 300 men can build three li about one and a half kilometers. That means a thousand li, or about 530 kilometers, would take 100,000 men one month to complete. So far so good. and so many. Most of the soldiers were stationed at the towers. The towers had a dual use to make the most effective the defense. The beacon tower behind me was not only the perfect vantage point for guards on this frontier to watch for the enemy coming from the north. It was a signalling station. So, when the enemy was sighted, this beacon would have been ignited. 'This is how it worked. As soon as a guard spotted nomadic warriors he transmitted smoke signals by daylight or beacon fires at night. The alarm was communicated along the wall to guarrisons located in the hinterland. How long is the Han wall? Only recently have Chinese experts started to find out. We will join the local archaeological survey team who are taking part in a national survey. to locate and ??? of the Han ??? A team is heading out into the Gobi Desert. They need a whole summer just to measure this section of the wall. At noon, the temperature can climb to over 40 degrees Celsius. Today the team is exploring a fortification that lies in the hinterland of the hard wall. This could have been a garrison for support troops. Today the remais are hardly visible. This tower has a name, it is called "Half Tower" obviously because half the tower is missing. The team are here today to locate the fortifications with GPS. I 'm wondering how they are going to measure the height, because it is so crumbly, I'll ask him. (In Chinese) So, they don't have to climb up the tower to measure it. They have a device here. A laser rangefinder collects the data. It will be a few years before the results of the survey are summarized and a figure can be given for the length of the Han wall. So, from here to the Jade Gate is about 45-50 kilometers and there are three sections of the wall that are quite visible and in between there is virtually nothing although the archaeologists may find traces. Mr. Young is very reluctant to give a guess estimate of how many kilometers of the Han wall are standing. GPS team leader, Mr. Young, has given William directions to a place in the desert where the wall has a unique shape. It is a 16 kilometer hike so William is buying provisions for the trip, at ??? market. Well, raw meat would not be very good in the desert. A lot of what he sees doesn't seem too useful for a desert track. but he finally finds what he needs. Successful shopping trip, for 1.99 or so, a good supply of high-energy foods. Hmmm... delicious. Next morning, at 5 o'clock, Lindsay sets off for the hike. Lots of satellites... It is 14.4 so, it is about 9 miles or more... He is not walking alone. In the desert it would be too dangerous With him is his Chinese friend Piao ??? Their GPS says they will reach the unique strip of wall in five hours. It is cool now, but the sparse vegetation is tender-dry. There has not been any rainfall here for months. They are walking in a featureless landscape. Consider a solitary tree over there. Back in 1987, I just had a big map of the whole country. Basically, my journey along the Wall from the desert to the sea was like that. 1,700 miles, not the ideal map for hiking across desert grassland. It is nearly noon and the Sun is burning. but finally they arrive at the place they have been looking for. There it is! We made it. Ah ah! At last! Great! Brilliant! For William it is already worth the trip even the five hours back . Amazing! Oh, look at that! Fantastic! Of all the faces that the Great Wall of China has this is the rarest of them all. This wall is made of wood. It has six layers of branches there and in between minimal use of the gravel so, I am really glad I have come here today a well worth a 10-mile track. Leaving the Dunhuang region and making his way east and on the ancient Silk Road William is aiming for a town called ??? The historic site is five kilometers out of town. And the best view is from the sky. A giant castle guarding the Wall built in 1539 by Jiajing, emperor of the Ming dynasty. The Ming emperor's contempt for the nomads reached grotesque proportions with the demand that the character G standing for barbarians should be written as small as possible. After the Han dynasty, other dynasties rose and fell. Many of them build walls but none of any significant length. Ming emperor Jiajing ascended the Dragon throne in 1521. He renewed the Han tradition established in ancient times constructing a long wall at the northern border with its westernmost point at the Jaiughuang Pass Jaiughuang translates as Barrier to the Pleasant Valley. and Pleasant Valley means China. This gigantic fort is build in the foothills of the Hymalayas. In the courtyard the mighty walls form a kind of maze to stop invaders in their tracks. And there is a wonderful legend about its construction. To avoid wastage of materials prior to construction of the fortress, the architect was asked to calculate exactly how many bricks were required. He computed 999,999. The bricks were delivered the fortress built and at the end, the chief of works confronted the architect with a brick and said, "This is wasted". Bur the architect was too smart. He said, "No, I factored that into the equation. "That brick should be placed over the portal "and it will bring all the guards in the fortress "and all of those travelers passing under these portals good fortune". Six hundred years later the leftover brick still remains. Next to the fort is the starting point of the wall constructed by the Ming. This wall has nothing in common with the brick and stone wall north of Beijing. It is made of rammed earth and although is more than 400 years old it is still in good shape and it is still wide enough to walk on. On his walks along the walls William Lindsay soon learned he could count on receiving warm hospitality from the farmers along the ???. Before coming to China my family and friends were very concerned in 1987 going to China, the big communist country on the other side of the world all the people going to be friendly and I didn't have a support crew with me. I depended on farmers. I discovered very early on the farmers were my great allies even with very little Chinese but a lot of sign language and smiling I got what I needed, food, water, shelter. Without them I could not have been successful. Even if many of them can't understand why a foreigner shoud be so interested in the Wall. For them, this is no monument but simply a part of their village and one with a perfectly practical use. I was asking him why these holes in the Wall. I thought they were nests but in fact, previously, the farmers were right up against the Wall so, there were wooden beams going into the Wall but the Great Wall experts, the Cultural Heritage Protection authorities requested the farmers to destroy these buildings and move back in order to protect the national heritage If you want to know how Ming dynasty masons constructed their wall more than 400 years ago, all you have to do is keep your eyes open. Even today Chinese farmers build walls in the same way their ancestors did. They tamp the earth in a wooden casing tamp put layer on layer. They even sing the traditional folk songs passed down from their forefathers. A house is not complete without a wall around it. says an old Chinese proverbe. My friend Chan is building his wall to enclose this compound so, this is the final piece of work and this is embedded in Chinese architectural tradition whether it is a compound or a village or a kingdom. It must be enclosed, completely safe. They build most on the main wall just like this, it is a rammed earth wall. Imagine how many billion thuds it took The singing is an important part of the work. It keeps all the rammers in step of the beat so, they are all in step going along the wall they get into a rhytm. The actual content... Oh, I have been in China 23 years and this guy has a really heavy accent. It is a bit difficult. But it is definitely a kind of rap. It changes the words and occasionally you hear them chuckle, so, I think he gets a little digging about those who are kind of falling behind in distance or maybe he can tell by the thirds if someone is answered cheer. This group of about 20 farmers, mostly women, took a day to erect about 27 meters of wall. We don't know if their ancestors could have worked better or faster but we do know they would have used the same materials and tools except for the tractors carrying the clay and the cell phones. On his journey along the walls of China William Lindsay is walking eastwards out of the Hershey corridor and turning north along the Great Wall of the Ming dynasty into the great loop of the Yellow River, the cradle of China's civilization. This is always been the gateway for the nomads to enter China. Here though wind and weather have done their worst the wall and its towers can still be made up on the crags above the river. The ??? and forts were the outposts of this defensive outer wall. Today, their use is strictly non-military. I love staying in the countryside. This building is made of thick blocks of limestone and on the roof there is turf. Then you come here in winter, we have a good method for keeping you warm. You see this? It is not a bed, it is called the kang, k-a-n-g. And they put the fuel here, light it — you can do the cooking here — you have got a nice bed for the night. So, I have got full board and lodging breakfast on morning and dinner this evening and lunch coming up soon for less than 10 dollars. I should apologize for the slurping. It is part and parcel of eating in China considered the sound of an appreciation. The ingredients of the lunch William is appreciating today are also the reason the nomads raided the land of the Yellow River throughout the 16th century. In the year 1549, the barbarians come to plunder. But the nomadic cavalry ??? to a virtual standstill at the new border wall at Chuan Fu. The wall stands fast and the nomadic troops are unable to capture the Chinese granary. Does this mean defeat? The barbarians do not give up. They have a message for the Chinese. They will attack Beijing, the capital. By marching east, the nomad army finds its way around the wall, thus avoiding the Ming emperor's elaborate border fortifications. No one had suspected the nomads could cross the natural barrier, the mountain range north of Beijing. Back in 1550, the nomads did not meet with any serious opposition on their way south. They terrorized Beijing suburbs for three days. They demanded trading rights leaving the Forbidden City untouched before drawing back to the steppes. After a short period of trading, the Ming emperor started building a wall of stone north of Beijing. Between the 1550s and 1644, it reached a length of at least 1,200 kilometers. The Stone Dragon, the Chinese Great Wall, as the world knows it today. How many people were needed to build it? Official figures are rare but in some inaccessible sections of the wall there are still stone tablets engraved with texts that could give us that information. I am hoping this stone is going to tell me something about when this wall was built, how many people were involved and mention some place names. From here, the inscription looks very faint but we have a ladder, master artisan, Mr. Hou and with his simple tools we are going to copy the stone and produce a rubbing which hopefully will reveal the full content of the tablet. This ancient Chinese copying technique starts with gluing a sheet of paper onto the tablet, simply with water. This is step number one. Step number two, ??? translates literally as typing characters. So, he is using a brush and he is hammering the paper into the carvings. The higher parts of the paper will be blackened and the lower parts that have gone into the characters and any design along the edges they will remain white. After three hours of spounging and drying, Mr. Ho presents his piece of art. It looks like a blueprint or an old archived document. And he helps William translate the ancient Chinese characters. which today hardly anybody can read. This stone is telling us that two military officials in charge of 1,100 families, put in the effort to build 250 yards of wall in the autumn of 1579. So, in terms of very simple arithmetic productivity, we are talking about four persons per family 4,500 people working for 8 to 10 weeks in the autumn of 1579 to build that. Whereas the tamped earth walls were built by untrained serfs or peasants this project required special knowledge. Hundreds of master builders and skilled engineers, thousands of stone cutters and tens of thousands of masons were recruited to build the wall. And another factor led to the costs rising exponentially. Tamped earth walls were built using materials available on site. The material for the new wall had to be manufactured before use. The Chinese had devised a network of brick kilns set up near the construction sites. One of these sites was found by local farmers and inspected by Professor ??? curator of the Great Wall Museum in Jiayuguan. So, at this location they discovered around 60 brick kilns and its ranks as the best production centre of bricks preserved along the whole length of the Great Wall. It is estimated that each kiln could fire 5,000 bricks. Now, given that there are 60 kilns in this valley the production of this center alone would be equal to 300,000 bricks per month, industrial scale production. Mass production is one thing but it is a different matter to transport the product to where it is needed. Logistics. Now, key question, very interesting question is how did they move all the bricks up there? Again, there is almost no historical record to answer this question. But Professor Huang has his theories. People may have carried a few bricks on their backs, like this. And also it has been suggested a herd of goats could have carried a lot of bricks up there quite effectively. Two bricks on the back of the goats and the bricks were joined together with rope, so, the goat is quite balanced as it is moving up the mountain. Even without bricks on your back it is a hard slog up to the wall. But it is worth it. Hardly any tourists makeit to this isolated section. Every time I come up here on these trails ??? the builders, who had so ??? all of these building materials up here, all of these blocks, all of these bricks. The sometimes bizarre roots taken by this wall has led many experts to believe that more than just defensive considerations were in play here. For generations, the Chinese had followed the practice of the Feng Shui, the teachings of wind and water. Feng Shui experts were ^probably consulted and obeyed before the building of the wall to make sure that the forces of nature would work in its favor. Spending his days alone on the wall Lindsay imagines how the soldiers must have suffered here, cut off from the world, enduring winds and foul weather, squeezed into bare and cramped quarters for months on end. Finally, this wall is a monument to the close world view of the Ming Empire. It circumscribed their universe and excluded everything ??? Often scratching around in this rubble you can find bits of pottery. I'm not sure if this stone is... Interesting, maybe a griff on it. It might be... Ah! That is a stone bomb that would have been packed with gunpowder a mud seal a fuse, and the trowels were packed with these maybe 50 or 100 to be lobbed off the wall when the tower was attacked. That is a really good find. 320 km further east, we find another example of living history This is John Ho Chan. His ancestors built a wall here 440 years ago. Close by, towers have other family names like the Chang Tower or the Wang Tower or the Lo Tower. Here we have the family history of the Great Wall. still living on 440 years after it was built. Even today, they still worship their ancestors by celebrating ancient festivals. Other '??? was ??? she should be quite nice, fresh pork. It would have been a rare moment of relaxation and abundance in a hard life. As the oldest member of his family, Mr. Jam makes the sacrifice to his ancestors and burns incense sticks. Then the living generations of the Jang family bow to the dead and to their own great history The village families had to look after and feed the soldiers in the towers. Their takeaway food service survives to this day. Jang the farmer, down in the village prepared some delicacies for me. So, munch on up here after my hike. It is amazing to think that 400 years ago guards garrisoned up on the wall would be sent this by the families. It is a loaf, it is a kind of pastry kept fresh in one of these large oak leaves. You can see the leaf prints on the pastry. Let's have a taste. Hmm... Full of trives. Kind a Chinese hamburger, maybe the original Chinese takeaway for those up on the wall. By 1644, just short of a hundred years of construction the most impressive defense wall ever made by men, was finished. However, it was not one single Great Wall. It comprised a system of several defense lines from the mountains to the sea. In 2009, after a national survey of the Ming Wall Chinese officials announced that the total length is 8,850 kilometers. This is the end at ??? meaning Mountain Sea ??? The Chinese liken the Great Ming Wall to a dragon sneaking across their land and here it comes to a geographical end at the dragon's head of the Yellow Sea. Not far from this location, in 1644, the commander of Shanghai Guang faced his biggest challenge an event which led to the end of the Great Wall functioning as a national defense. Professor Huan is taking William to the gates of walls in the outskirts of Shanghaiguan. This is the place where the Great Wall story came to an end. The construction of the Great Wall led to the financial and strategic collapse of the Ming dynasty. Revolts broke out everywhere in the Empire. An army of rebel peasants marched on Beijing where they toppled the emperor. Then on to Shanghaiguan the last stronghold of the Ming Empire. But a mighty army had risen from the steppes heading for the Middle Kingdom. The Manchus. Caught in between, ??? He was the general in command of the fortress at Shanghaiguam Now he was under siege. What could he do? This was a powerful garrison. But was it powerful enough to fight off attackers on two fronts? Professor Huang tells William Lindsay the solution he found. Trapped between two enemies, commander ??? knew he could not defeat them both so, he came up with a plan, to offer an alliance treaty with the Manchus in the north and the two armies joined and confronted the peasant rebel army and they defeated them, A wall is only as strong as the men who guard it, Genghis Khan is supposed to have said, his successes from the steppes the Manchus would have agreed with him. 80,000 Manchu soldiers passed through this gate. and answered the heartland of China The Manchus founded a new dynasty which in effect ruled over the Middle Kingdom until 1912. They called themselves Xing, meaning "the Pure". And the Great Wall was of no use anymore. But its story did not come to an end, Even today nobody knows how long all the great walls of China really are. There are still many more walls and stories to be discovered. And William Lindsay will not stop walking the Great Wall until he knows them all. I don't think in future so many people will be organized in such a methodical way to create something that was not just history that not just fell apart but is left as part of the geography of China and the world. Certainly in future, there are goint to be new wonders, communications, longer life, exploring planets, but in terms of blood, sweat and tears the Great Wall of China I think is the ultimate and that is why I am continuing to understand it. into companies of about 250 men each. And they are going to build for him 70 towers in that year. That means that each company has to build one tower every five days. These men have got to work day and night without stopping for the entire year. But Qi had the great advantage of using the troops that he had disciplined, trained himself, and brought them up. And he could rely on their competitiveness to build the wall within the time limit that the court had given him. The Great Wall project is more ambitious than anything the Ming Empire has ever undertaken. By the late 1570s, it is consuming more than three quarters of the government's income. But there is another cost that doesn't appear in the accounts - the human cost. They were, you know, far from their families, they were just working together as an entire unit. It must have been extremely hard, extremely difficult. Very, very heavy work and exhausting beyond speech. The pressure is on Qi to deliver. And the one force he knows he can keep driving as hard as he needs is his own army. But there are limits. Malnutrition, exhaustion and disease take their inevitable toll. And for those who die far from home, fellow workers become family... ..scattering token money to pay for a friend's passage to the next world... ..to rest at last. "We buried Fong today. "He was from the south, "like me. "He had a family... "..somewhere. "My love, "we're so hungry and exhausted all the time. "I sometimes think death would be a relief. "But that would be a betrayal of you. "So I carry on for your sake. "I've heard they'll make us stay and serve "on the wall when it is finished, "so even if I survive building the damn thing, "I may have to stay and defend it." For centuries, workers like Geng Zhou have been the forgotten heroes of the wall. Who they were and where they came from has rarely been recorded. Histories of these men have been almost totally unknown - until now. Wang Tao is an archaeologist from London University, used to digging in the ground for evidence of the past. In the Great Wall, he faces a challenge. The most revealing insights are found not so much in the bricks as in the descendants of the people who laid them. And that is what he has come to find. Outside a village to the east of Beijing called Dongjiakou, he takes a tour with local historian, Zhang Heshan. Zhang takes Tao on a climb 1,000 metres up and 500 years back to the heart of the wall-building project. The past here lives because of the efforts of men like Zhang. 40 years ago, he discovered the building records of each tower carved on stone stele inside. The stones themselves were removed during the Cultural Revolution. But not before Zhang had made copies. (SPEAKING CHINESE) The most important stone stele was placed in one of these, uh, towers just over there. And the names of all the important officials who are involved in this construction are recorded here, including General Qi Jiguang. And on the back, there are all the names of the ordinary workers - builders, carpenters, all related to the re-construction. And their descendents may actually live in the local village, become a part of the local history. The end of the climb is what Zhang is most proud of and what makes this section of wall unique. Every single tower in the district is named after a family in the village. (SPEAKING CHINESE) Mr Zhang is saying this is called the Zhang family tower, and it's constructed by General Qi Jiguang. (SPEAKING CHINESE) He recruited about 9,000 soldiers from the south, from Zhejiang, Yiwu. And Mr Zhang's ancestor was among those 9,000 soldiers. This is why this one is called the Zhang family tower. (SPEAKING CHINESE) The actual lives of the soldiers can only now be reached through the folk-memory of the villagers. And because every village name has a tower and a history to go with it, Zhang has started recording the oral history of the entire village, one family at a time. Starting with Mr Loa Jianhua. What's interesting is that Mr Loa's great great grandfather's tomb is still there, very close to the wall. And that can go back to the Ming Dynasty. They have about almost over 20 generations all lived in this village. And they've all come here, they were southerners and they actually, they didn't mix up with the northerners, the locals. And a story they were talking about was that one year, there was a famine and no food, and all the locals were coming to the wall to the Zhang family tower and the Loa family tower. They were all kind of fighting over, basically it's fighting over very little food to survive. And I can probably imagine that many people probably would die. For any monumental project, team discipline is vital. And when it breaks down, for whatever reason, it must be seen to be restored. Examples, however painful, must be set... Faster! ..for the good of the wall. Get them on their knees! Heads down! Draw your swords! What's going on here? Why have you stopped working? Put down your swords! Sir. There was a fight. We're making an example of the ringleaders. But don't worry, sir. We'll make up the lost time. That depends on how many times you have to do this, doesn't it? Haven't you enough to do, without fighting? You! What's your excuse? We haven't got enough food to go around. We are worked to death and treated like slaves! Is that what we are? No. You are my soldiers, paid workers. All of you! We only get half what we're owed and what's the point of money when you're dead? You are working to protect the Empire! Yes, there are hardships. But as a soldier, I am prepared to sacrifice myself, my life, to protect my home and my people! Those of you who have fought with me, you know that! You know what it means... There is not a man here who would not die to protect our families and our homes! But they are a thousand miles away. All we see is bricks and stones. This is not a battlefield. It is not even our home! This is just one long headstone for a million graves! On his knees! Bring out your swords! Sir, on your command. 'The wall will not build itself.' 'And it will not defend itself either.' Send them back to work. And get them some food from somewhere. I don't care where. Ya! Put down your swords! Set them free. Qi's new design was, in a way, revolutionary. It used a new structural form. But Qi realised that without the men to build it, and to exploit its potential, it was absolutely nothing. Qi issues orders for soldiers' families to be allowed to join them and settle along the length of the Great Wall. Having once turned farmers into soldiers, he returns those soldiers to the land to live, build and fight for their homes. The fact the men like Mr Loa are here shows the policy worked. But as Wang Tao discovers, its success owed much to the resilience and fortitude of the men themselves. At Dongjiakou, starvation had threatened the lives of the soldiers, and the future of the project, until Mr Loa's ancestor saw a solution. (SPEAKING CHINESE) When his ancestor first arrived here, there was a food shortage and people were fighting over a very little bit of food. And then they discovered the apricot trees. Mr Loa's ancestor and other soldiers began to gather the wild apricots for food, and later on, they decided they would plant them so they gathered loads of them and they planted them all along the wall. And so as you can see now, the whole landscape and the whole mountain is full of apricot trees. And for Mr Lao's ancestor, the gesture he inspired not only averted starvation, but ensured the Loa family would be here for centuries to come. The grave of Loa's ancestor lies directly beneath the family tower... ..its inscription barely visible after 500 years. But for Wang Tao, it's a chance to connect with an actual wall builder. This is extraordinary, it's Mr Loa's family or ancestral tomb. And the title here, it actually says, "the important or highly important ancestor, Lord Loa was buried here". And obviously Mr Loa, his ancestor, was the garrison commander of this tower. That's why it's called the Loa family tower. This is a family, personal story, which I have never known, and now, standing together with Mr Loa, the descendent of the soldier Loa, close to the Loa family tower, I think it's just bring me really back to the whole history and also the people who kind of, as part of the wall... And I feel a kind of... I'm becoming part of this as well. Today, the entire Loa family comes to honour their illustrious ancestor with offerings for his spirit... ..and to plant, in his memory, a single apricot tree. A memorial to one soldier who helped build the Great Wall. By 1575, the first sections of Qi Jiguang's wall are complete. Hs dream is becoming a solid and impregnable reality. On it stands an army he has trained to exploit its strength... ..an army now 20,000-strong... ..devoted to him. The young soldier who once dreamed of serving the Empire has now created its ultimate defence system. Not only is it the most ambitious, it is also the most expensive project of the age. And with the hopes of an entire dynasty riding on its success, it had better work. By the mid 1570s, the Great Wall is advancing at a rate of a new tower every five days. Yet Qi Jiguang knows it will be tested by Mongol attack long before it is complete. In the Beijing archives is a remarkable set of maps, showing how Qi's Great Wall defences were designed to work. Out to the far northwest, you see a pass between two mountains through which the Mongols would normally trade or raid. Then you have a series of outward observation points. Then you have a series of beacon towers, signal towers, and they're on the top of a range of hills. Then you have the Great Wall with all the forts. Then, behind that, are the headquarters of the various brigades of Qi's soldiers. If there was an attack, they would march out to the Great Wall to defend it, or even go further. So what Qi was able to develop was a very complex system. The wall functioned in different ways. And the men had to have an understanding of their function in the total system. Guangzhou is now part of Qi's defence line in an observation unit in front of the wall. One of Qi's greatest innovations is to introduce cannons, copied from Western models and now manufactured in China, an integral part of wall defence. The unit's job is to intercept and slow any attack while at the same time alerting the wall defences. No-one knows how well this new system will work. But on this March day in 1575, the perfect opportunity to find out materialises from out of the steppe. They're coming! Get yourselves organised! While Mongol raiders charge towards the outer defences, on the wall, the alarm signal triggers a well-rehearsed response. Men and cannons are mobilised in minutes. Fire now! The job of advanced units is to try to slow the attack. But the Mongols keep their eyes on a bigger prize - settlements around the town of Dongjiakou... ..where Qi Jiguang himself happens to be stationed. Inside the wall, the warning system has alerted the main garrison, and a counter force is mobilised. This is the moment of truth, for Qi and the wall. Whether the attacking force might try to scale the wall or break through the unfinished sections, no-one will ever know. The historical records recount that Qi's force was able to meet the invaders beyond the wall... ..where his superior forces could be made to count. The history also recounts Mongol prisoners are taken, including the brother of Mongol leader, Chang Ang. The battle of Dongjiakou is won and it is a defining moment for Qi Jiguang. He has proved that his Great Wall system works, with him at its head, inspiring the victory. At court, those who have criticised his project are silenced, at least for now, and the wall is declared a success. For his personal heroics, Qi is rewarded with two kilos of silver and the personal gratitude of the Emperor. It's an encouraging start... ..but Qi Jiguang is looking to the future. When his wall is finally complete, he will be the gate-keeper of the north... ..and potentially more than just another general. A few days after the battle, a chance to play the role of statesman appears, in the shape of Mongol leader Chang Ang, returning to the wall to bargain for the release of his brother. Is he still alive? Yes. If I were to make an offering to secure my brother, who is the man I must make it to? Is it the Emperor, through you? Or is it you? It's me. So what does it cost to get my brother back? Your brother can go free if we can be free of you. If you can guarantee that we will no longer have to pursue you and run you down, then yes, you can have him. Despite their agreement, the same tribe will renege on its deal and attack again. But again the wall will defeat them. Unbreakable, its brooding power sends a clear and unmistakable message that the Ming empire can and will defend itself. And over time, the growing security brings something new to the border. The first signs of peace. On some of the towers in Dongjiakou, there are the unmistakable marks of domesticity... ..clear evidence that some soldiers had the time and inclination to decorate their homes. Perhaps, as Wang Tao believes, under the influence of their wives. Before I came here, I thought these towers were just military towers. When I came here and visited these towers, I feel it's home. Of course, it has its function as a military device, but if you look, both sides of the wall, you actually see, no, it's not. It's actually very much a part of people's life and home life. Because when you look down the cliff, you're looking out on fields, and you see a wife with young kids, and then we can see, in Chinese history, it happens all the time, people being uprooted, re-rooted, and I think the Great Wall has re-rooted so many people and has created a new life for so many people. Geng Zhou is now a senior member of Qi's garrison and has settled his family in the village below the wall, now part of a new and growing frontier population. In what was once only a conflict zone, inhabited by raiders and soldiers, agriculture thrives and the population grows. The peace dividend of the Great Wall. It gives Qi the confidence to demand the funds to finish his great project. So far, only 1,200 of his planned 3,000 towers have been built. The wall will only continue to work, he warns the court, if he is allowed to complete it. However, in Beijing, the cost is already ringing alarm bells. So far, 1,200 towers and 1,000 kilometres of wall have consumed 550 tonnes of silver, two-and-a-half times the treasury's income for the last decade. For many, it is proof that Qi's project was always over ambitious. Basically, Qi had, in a sense, solved the problem. But still, when it's successful and you can keep the peace for 15 years, then people start to say, "Well, why are we wasting so much time, money and effort "against what is essentially a nuisance?" Maybe just a few raids by Mongols. Well, that was not going to be too problematic. Oblivious to the court's concerns, Qi looks ahead to the next phase. He turns once more to the man who has always supported him, who has always pulled the strings in court to provide him with funds - grand secretary Zhang Juzheng. But the more Qi demands from Zhang and the more Zhang tries to give him, the more their power is seen by the court as a threat. Qi and Zhang Juzheng had their enemies at court. They were just simply waiting, biding their time. And at last that time has come. There is a new emperor on the throne who listens to these new councillors. The great danger, as was always the danger throughout Chinese history, was if a powerful courtier linked with an equally powerful general. In Chinese, that was the military and the civil getting together. This is what always brought down a dynasty. Looking for ammunition to destroy the Qi - Zhang alliance, their enemies find it, in the Great Wall financial records. Great secretary. I hope you're not going to ask for more money. I can't help you. Do you know what they're saying about me? "Grand secretary Zhang has cheated the imperial person. "He has plagued the population with taxes, "accepted bribes, sold government offices and advanced his henchmen!" That's you, by the way. What did they say about me? I said, "Majesty, those henchmen preserve the Empire "and your imperial person in continued safety." What do they want? They demanded protection. Well, protection costs. You only know it's worth paying for when it doesn't work. Tell them that. Tell them we need more towers. Don't even think it. There is an indictment for me for charges of corruption. Did you know that? All it needs is for the emperor to sign it into proclamation. And what am I supposed to do? If I were you... ..I'd stay away from me. As the emperor's former tutor, Zhang is spared prosecution... for the time being. But for the next few years, Qi's ally remains under attack until, worn down by the ceaseless strain, Zhang Juzheng dies. The partnership that built the wall is broken. Now with his only political ally gone, Qi himself is open to attack. And the most effective weapon at his enemy's disposal is his alliance with Zhang. A provincial examiner in Zhang's employ confessed that Zhang had placed before candidates to imperial office... In court, Zhang's crimes are re-examined and a conspiracy with Qi is discovered. A clear attempt to create a suitable atmosphere for an impending takeover. Furthermore, and I quote... "General Qi Jiguang is to make his army available." We can only surmise what for. That before his death, Grand Secretary Zhang Juzheng had plotted to take over the throne. I find it hard to believe that my old tutor had the intention of usurping me from my throne. Yet it is clear that he and commander-in-chief Qi Jiguang have had the capacity to do so. This is too ominous to be ignored. I mourn the loss of Grand Secretary Zhang and can only assume that he has been blinded in his old age by the overwhelming ambition of Qi Jiguang. He has violated the divine principle of balance. We have had enough of Qi's demands. We have had enough of walls. Stand by! One! Two! For years after Zhang's fall, life on the wall has gone on as normal for soldiers like Geng Zhou. Yet Qi's political enemies in Beijing have not been idle, and now they are now ready to make their move. Qi has years of correspondence from Zhang in which he promises Qi his personal support and hints at deals done behind the scenes. Words that in the wrong hands could be twisted to look like conspiracy. So Qi puts them beyond reach. And a lifetime of friendship and the record of their wall-building partnership is erased. It was Qi's ambition that drove him to build the wall for the sake of the empire. Today is your first position. Now the Empire fears that ambition so much it is ready to get rid of him. Go. The only question that remains is how they will do it. If a case of treason can be made against Qi, he will be summoned for trial and public disgrace will be followed by private execution. But Qi is ready to defend his record. Regional Commander Qi Jiguang is to step down with immediate effect. He has underestimated them. There will be no trial, no chance in court to speak the truth. Just quietly sacked. (SHOUTS) For common soldiers like Geng Zhou, the end of Qi defies all reason. The army is losing its father. General...? 'He doesn't remember me. 'The great captain is gone.' Qi Jiguang retires to his home town. Within the year, he is dead. He leaves behind 1,000 kilometres of Great Wall and towers, the most comprehensive defensive line in China's history. But still not finished as he intended... ..and with him no longer there to make it work. Qi Jiguang was the heart and soul of the wall. You needed a man with Qi's vision to use the wall not only as a static barrier but as an offensive weapon against the Mongols. Once Qi was gone, then the Ming just retreated behind the walls. The real problem then was the Ming did not know what was happening outside the wall. Outside the wall, the Mongols were teaming up with a new enemy. The Manchu empire - the next dynasty in waiting. It is 1644, more than 50 years since the death of Qi Jiguang. The Great Wall system he built still stands. Yet behind it, the empire is crumbling... ..crippled by the weight of defence costs. Now corruption in court, neglect of defence and peasant revolt push the Ming dynastyto the brink of collapse. And beyond the Wall, the Manchu army is coming. The Manchus were a much more organised and unified force than the Mongols. They moved in systematically. They launched raids on China in 1636 and 1638 as they moved in on the Chinese Empire. Sweeping down from the northeast, the Manchu approach the Great Wall at Shanhaiguan... ..where historian David Spindler enters the town from the Chinese side, heading for the most fortified gate in the history of the Wall, once called the First Pass Under Heaven. It is here on May 27th, 1644 that the Great Wall is finally breached... ..without a single drop of blood being spilled. On the same day, 500 kilometres west in Beijing, Emperor Chongzhen, the 16th Ming emperor, leaves his palace for the first and last time in his life. His empire, riven with rebellion and corruption, is bankrupt. He is drunk. In the spring of 1644, the capital of Beijing was taken over by a Chinese rebel leader. So, at that time, the Chinese Empire was not a functioning entity. The country was really in collapse. With the Manchu army approaching Shanhaiguan, inside the town, Chinese rebels have taken control and the garrison commander is ordered to surrender. His back was quite literally up against the inside of this wall, and he called for help from outside of the wall, which was quite ironic, because the people outside of the wall are the ones that it was built to defend against. The most impregnable defences in China's history, never once taken by force, are now opened to let the enemy inside in a last, desperate bid to save the failing empire. This is an exciting place to be, because I know that this is where it happened. I'm in one of the three places through which the Manchus streamed on May 27th, 1644. They overran the country and they stayed, and they ruled China for the next 200 or so years. (SOBS) As the Ming era closes, the Great Wall experiment closes with it. The coming centuries are marked by more outside threats. Yet this time, invasions do not come overland from the north but from the wider world across the oceans. And so, for hundreds of years, the fabric of the wall decays. Today, the skeleton of the Great Dragon is all that remains of the beast that once lived. But its spirit lives on... ..not just in the bricks and stones now being restored across hundreds of kilometres, but in the great wall of iron and steel, the modern army that protects China today...