So, let’s first disabuse ourselves of the notion that the purpose of the northern wall chain(s) was ever, really, to “keep the barbarians out.” That is fundamentally not what they were ever conceived to (much less successful in) doing. Rather, the walls – from the Qin, to the Han, to the Tang, to the Ming – were only every designed to serve as a way to funnel the steppe raiders into predictable and defensible regions where they could be better managed. The walls were only one piece of a far broader and more comprehensive system of mutually overlapping defensive structures and strategies meant to bog the “barbarians” down at the border and limit their penetration into the “heart” of China – certainly not some attempt to “stop them cold” at the border.
How do we know that the Chinese weren’t particularly interesting in building a wall to stop illegal immigration? Well for one, because from the Han onward, one of the central policies the Chinese court had in dealing with troublesome groups of non-Chinese along the border regions was to capture, transport, and resettle them deep within Chinese territory in order to diffuse their cultural “otherness” and render them as Chinese as possible as quickly as possible. This policy – sometimes referred to as “cooking the barbarians” (as in, rendering them into a civilized form) - was one of the lynch-pins of foreign policy during the Han and even Sui and early-Tang. And it, in turn, illustrates the pre-modern conceptions – or perhaps more accurately, lack thereof – of a given or fixed ethnicity.
Quite to the contrary of what most of us in the modern world understand as being “an ethnicity”, such a concept would have been quite foreign to many – if not most – pre-modern cultures. Rather than being some blood/genetic based fixed value, one’s culture was during the period before the late-8th century in China, based primarily on one’s actions, dress, and comportment. The old saying of “if it looks like a duck and quacks like a duck, it’s a duck” is not inappropriate here. Prior to the 750s or thereabout, dressing, speaking, and acting Chinese could – over a long enough period of time, at least – make an individual or group understood to be just as Chinese as anyone else. That was a major part of the policy of resettlement: we’ll relocate the barbarians in China proper, educate them in our obviously superior ways, and then – after a long enough time – they’ll be Chinese. This is what happened with the major scourge of the early Han Dynasty, the Xiongnu Confederacy, as well as later threats from the northeast like the Xianbei and even the various clans of Turks that existed along China’s periphery – when and where they could, they’d be resettled deep with China borders… sometimes dispersed, but just as often in specific enclaves set aside for such ventures. And as for the children of their leaders – what we might think of as being “princes” – they serve simultaneously as hostages for good behavior and eventually cultural emissaries by being sent to the capital city (whichever one happened to be in vogue at the time, but typically Chang’an) and educated in the fineries of Chinese culture.
And as for the groups that were either a bit too rough around the edges, or just weren’t willing to submit to relocation – well, the Imperial court had a solution to that, as well. It was a policy known as yiyi zhiyi, meaning “use the barbarians to deal with the other barbarians.” In short, the non-Chinese people deemed “too uncooked” to be brought into China itself for finishing school were instead kept at the border and pressed into imperial military service. Their job would be to act as border guardians, since their tactics and battle strategies so closely resembled those of the various hostile groups they were now pitted against. Even the generals and commanders of these border armies were typically not Chinese at all, but rather the “Sinified” sons of captured foreign nobility. One particularly notable example is the commander of the Far Western Protectorate of the Tang Dynasty (what is today known as the Tarim Basin in northwest China). Known in Chinese as Gao Xianzhi – though born as Go Seonji. The son of a defeated general of the northern Korean state of Gojoseon, Gao served in the far west and consolidated Tang rule over the whole of the region, even serving as the supreme commander of the Tang armies that fought (and lost) the one and only battle between China and the Abbasid Caliphate along the Talas River in 751. I realize I might be at risk of getting lost in the weeds here, so I’ll pull back; but the point of this is that at least through the first half of the Tang, the point of foreign policy was to sinify – make Chinese – the groups of people surrounding the “Middle Kingdom” by bringing them into the fold in a controlled manner.
This would largely remain in effect – and with it the ideations of “otherness” being cultural rather than in-born - until round about 755-765, with the breakout of what was one of the largest civil wars in Chinese history – the An Lushan Rebellion – in which the most powerful general in all of the Tang Empire, the Sogdian-Turk An Lushan, marched his Army of the Northeast against the critically underdefended emperor and capital, forcing the flight of the imperial court to Sichuan, and resulting the near-total destruction of the great city. That engendered real feelings of racially-based animus for really the first time at a societal level, and crystallized the notion of there being a blood element to Chinese versus not-Chinese. This was shown during the court’s flight to Sichuan, when a Tibetan emissary group approached the imperial guard and asked for provisions, but were slaughtered for their trouble.
Getting back to the wall, though, again it must be remembered that it was never conceived – even in the Ming – as some unbreachable barrier to the north. Instead, it was a way to control and direct raiders to strategic, fortified hamlets guarded by heavily garrisoned forts of border troops. Because, ultimately, that was the threat from the lands beyond the border 99% of the time: small groups of border raiders looking for easy pickings, and who could be deterred by high city walls, strategically-placed defensive canal systems, and cross-bolts. The threat of large confederations of steppe tribes was, of course, an ever-present concern ever since the time of the Xiongnu during the Han… but they were rare, and Chinese foreign policy was very much geared toward preventing those from ever occurring. After all, it was far easier to buy off rising star among the steppe tribes with favorable trade deals, and proposed marriages to Chinese “princesses”… and then to turn those friendly and sated khans around and say now go attack that other group of barbarians and keep them out of our hair – than to allow them to put aside their differences and band together against the realm itself. Such a policy was both far more effective than, and much cheaper than trying to make some unbreachable barrier. So instead, the walls were there to redirect and control the patterns of raiders, not stop them outright.
That system – redirect and bog down raiding parties, and ensure that the steppe khans were too busy fighting one another, and paid well enough to not attack China – would work very well (with a few hiccups) through the first half of the Song Dynasty… until the collapse of the Liao Empire to China’s north and the surging forth of the Jurchen through Manchuria and into Northern China, causing the Han Chinese to retreat south. And to say that the Jurchen people – in their sinified form of government as the Jin Dynasty – were rather less-than-effective at managing the yiyi zhiyi policy would be… something of an understatement. It would be the Jin in the north and the Tanguts of the northwest (known as the Western Xia) that would so badly mismanage the other steppe clans that they’d allow the disparate and often mutually hostile tribes to band together under a certain Temujin and upend the order of the medieval world.
So the wall(s) worked fine at what they were only ever built to do – it was the policies of the governments managing those walls that so badly failed in the end.
Abramson, Marc S. (2008). Ethnic Identity in Tang China.
Chen, Sanping (2012). Multicultural China in the Early Middle Ages.
Franke, Herbert and Denis Twitchett. The Cambridge History of China, Vol. 6: Alien Regimes and Border States
Twitchett, Denis.The Cambridge History of China, Vol 05: The Sung Dynasty and Its Predecessors