Can you solve the mystery of the Great Wall?

Here is a mystery for you. The Great Wall of China is one of the architectural wonders of the world. Apparently not quite visible from space but very impressive nonetheless. Built and rebuilt many times over many centuries and by hundreds of thousands of labourers. The picture below shows you one of the most visited bits of the wall. The mystery is that the wall is so low at the top of the mountain: it is no more than half a meter high in some sections of the top of the hills, whilst it is a massive structure that is many meters high at the foot of the hills. The bit I walked on near Beijing had a huge fortress with massive walls at the bottom, and laughably short walls on top, no more than 2 kilometers away from the bottom.

Now, without cheating by looking it up online, can you give a good strategic theory for why on earth the wall is so low at the top of the hill but yet so massive at the bottom? I will give you my best guess on Monday. To be clear: this is not what you would see amongst the fortresses of Europe, where walls at the top of the hills are pretty impressive too. In Europe the defenders were clearly worried about keeping people out, whilst this is apparently not the role of the Great Wall of China….

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13 Responses to Can you solve the mystery of the Great Wall?

  1. conrad says:

    How about standard Chinese corruption — The laborers making the wall realized the officials checking on them would be too lazy to get to the top of the hill so it didn’t matter if they did a shoddy job there. And so they did do a shoddy job there.

  2. desipis says:

    I would have thought it would add movement along the wall to have it relatively flatter and smoother in comparison to the surrounding terrain, making it a safe and accessible transport route.

    Also, if you’re impeding movement of the enemy you don’t have to add much disincentive to the peak of a hill to make them prefer to try climbing the higher walls in the valley anyway.

  3. derrida derider says:

    To elaborate despis’ answer, the role of the wall was surely to move cavalry along it to meet threats – think of it as a fortified road as much as a barrier. Good fortification systems are designed for a mobile defence, not a static one (something the designers of the Maginot line actually understood – it was only ever intended to channel German attacks through Belgium where the best Allied armies could meet them outside France).

  4. Andrae Muys says:

    My understanding is that the Great Wall isn’t a wall strategically, it is a road. Its purpose not to prevent incursion (when you are defending a 2000km border that isn’t possible), but to respond to it. In this respect it has the same purpose as the walls of the Mid-Roman Empire. Small and Medium sized raids can cross the wall with relative impunity, but to no effect. Having spent a week or two raiding the border region, they will find upon their return that the wall is garrisoned by well provisioned troops that, courtesy of the fortified road, can at least prevent them escaping with their booty (reducing the likely benefit), and in many cases escaping at all (increasing the risk).

    Assuming the raiders are rational, this is an excellent strategy to reduce the garrison requirements against anything short of actual invasion.

  5. Oliver Townshend says:

    To keep horses out?

  6. Alan says:

    The Great Wall is not ‘many centuries’ old. It dates from the second half of the Ming dynasty. Previous dynasties built walls but the there was a no single unified wall until the late 1400s. The wall was never finished because the dynasty collapsed before the thing could be finished when an alienated general opened the gates at Shenhaiguan to the invading Manchu.

    The Qing dynasty did not need a wall because as much of their territory lay outside the wall as within. Ditto the Mongol Yuan who preceded the Ming. The Han, Sui and Tang did build walls but at strategic points rather than an attempt at enclosing the whole country.

    Qin Shihuangdi, who is supposed to have completed the wall during his brief dynasty, cannot have been all that active a wall-builder because his walls draw precisely 6 characters out of the tens of thousands of characters in the Qin official history.

    The wall is just not as ancient or as central to Chinese history as we are used to thinking.

    • murph the surf. says:

      If the raiders were the “barbarians” from the north then they would be have been expected to be on horseback so a small wall at the top of the hill suffices- the area perhaps isn’t horse accessible?Guards could deal with raiders on foot where the barrier is lower.
      Lower points at the base of hills needed to more developed as they also functioned as statements of power- and housed customs agents? Roads lead to check points situated in or near the wall.
      Plus with the benefit of those exam passing , long sighted civil servants in the imperial service there was a realisation that all the tourists of the future would need amentities blocks and those in the loop would need places to flog trinkets to the busloads of curious gawkers- thus plenty of space was built into the check points.
      My final observation is that the idea of moving along the wall is also less easy than may be envisaged from the photos- the area of the wall immediately around the bus parking I would guess have been modified to make access easier.You only have to go a short distance and the steps are about 1 metre high! It is a challenge just to go a couple of hundered metres.

  7. Sancho says:

    I’ve scrolled past the responses without peeking and I’m guessing…

    Hilltops are easier to defend against attackers, so those areas would be low so that the Chinese side could pass men and goods en masse at some point of the wall.

    Answer is probably far more prosaic.

  8. john r walker says:

    Chinese military history is not my area … pure guess … fortified walls , even fairly low ones, are difficult for cavalry to cross- they have to dismount and so on. By the time the wall is crossed and a hole knocked in the wall big enough for large numbers of horses to go through quickly, mounted Chinese troops could have concentrated at that spot for a counter attack on a opponent that was provably disorganized and not yet fully remounted. Also Guess that the high points along the wall were in areas that were less fertile, less populated and further away from the most profitable targets for raiders.

  9. Tel says:

    I was going to say about secure transport and gradient levelling but others beat me to it.

    It makes sense to put the keep on a hilltop because it gives maximum visibility and provides a nice beacon tower to call reinforcements. All through Europe and the Middle East you see that people prefer hilltops for placement of a keep. Once you build the keep, there’s a local zone of security around that (about the distance an archer can effectively hit a moving target) so the pressure comes off the wall builders.

    You also have to consider the damage that hit-and-run mounted archers can do from the hostile side of the wall. You have to make sure the wall at its lowest point still doesn’t offer good line of sight from any nearby mounds on the hostile side. This constraint forces you to build higher in the valleys, but doesn’t matter much on a hilltop where hostile archers don’t find a good target anyhow.

    Finally, there’s the “Security Theatre” aspect. Consider that most common commercial traffic will be following the valley and will cross the wall at constrained key points. So make a bloody big effort to put up an impressive gate on those key points… something that radiates the “don’t even think about it” vibe. Since news travels by word of mouth, everyone will describe the wall as impossibly large, because that’s the bit they got a good look at.

  10. JM says:

    You notice the wall follows a ridge? Will steep drops on both sides?

    If you’re using the wall as a defensive mechanism rather than a road – which only serves to get your troops in position – then there is less need for height at the top of a ridge. And in some respects a higher wall is harmful.

    The projectile weapons on your side have to clear the top of the ridge *and* the wall, and do so with sufficient accuracy to hit the guys on the other side. So you don’t want a high wall getting in the way.

    And if you have archers/whatever on the top of the wall they just need some protection while the attackers are struggling uphill. You get enough height from the terrain itself.

    Flat ground is different. The wall needs to be higher to gain an advantage for your archers, while it is less of a hindrance to projectile weapons located back from it at the same level as its base.

  11. Katz says:

    The Wall was built that way in order to render it invisible from the moon.

    US astronauts reported that this ruse worked perfectly.

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