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….

Author: paulfrijters

Professor of Wellbeing and Economics at the London School of Economics, Centre for Economic Performance

11 thoughts on “The mystery of the Great Wall?”

  1. Seems that perhaps it’s much tougher for enemies to climb up a hill an get over even a small wall – especially if they are trying to do it unnoticed.

    But the bigger picture which is alluded to in the post is that the wall is more of an intimidation factor to enemies – imagine the scale of forces required to build such a massive fortress, trying to attack in the few “easy” locations just leaves you outnumbered.

    My 2 cents.


  2. An intriguing puzzle.

    As i recall from history class, the main problem faced by those on the inside of the Great Wall – before the Great Wall existed – was that marauding mongol hordes would swan in on horseback, loot, pillage, and burn villages, perhaps sling a few women over their shoulders, and swan out again. These nomadic enemies were not interested in permanently acquiring and setting up camp in the territories they plundered: rather, they wished to steal surplus that had been generated by the hard labor of the permanent residents.

    So, my first thought is that the Wall’s main purpose was to keep out riders on horseback. Because horses cannot physically generate the (horse)power necessary to jump over even a short wall if it is placed at the very top of a hill, there is no reason to make the wall height in such sections of the wall any higher.


  3. To encourage attackers to concentrate their efforts at the hill? Presumably it’s lot harder to move a body of soldiers over hills than plains. While the attackers have one part of their force on one side of the wall and the other on the other side, defenders from the fortress in the low area below sally forth and attack them from one or both sides.

    Defenders don’t have the resources to defend all of the wall at once so they concentrate their forces at the weakest areas and encourage raiders to attack the strongest, e.g. high ground, the high ground also has the advantage of inhibiting fast movement.


  4. The wall is quite wide, maybe it also served as a road for reinforcements and messengers, they might have kept the slope low for transport purposes. (considering that it would be easier to defend parts on the top of the hills)


  5. Agree with many of the previous comments
    1. To lower the sloping grades for when using the wall as transport. I actually found the wall a bit awkward to walk along at steep parts.
    2. Because it is hard to lug stones to the top of hill to make high walls.
    3. Because with the height//uphill advantage from being at the summit, the extra height wasn’t valuable.
    4. The wall is really a psychological military tool anyway. If your scouts say it’s continuous for many kilometres (and they might not climb the hills anyway), then you might just turn back.

    I always found it odd you would build a wall at the top of a hill anyway, since hills are essentially natural barriers to armies.

    You allude to the idea that the wall was not designed to keep people out. If I recall, there are actually many disconnected ‘great walls’, which I assumed where simply because of different territorial conquests in different eras. Perhaps the wall served other purposes as well – customs (taxes on trade), facilitation of trade itself through mountainous regions, and so forth. Perhaps it was to stop people fleeing for some reasons.

    Off to Google now to see which is right.


  6. I think the answer is a combination of military, engineering and economics factors.

    In military terms, the wall had a strategic, not tactical, role. It was intended to prevent raiding parties entering the Kingdom. That means it had to hinder large bodies of mounted soldiers with their necessary baggage. Cutting the easy routes along the valleys would do that. Small groups of dismounted soldiers could penetrate the heights but they would be ineffective, have limited mobility and be easily mopped up by the defenders.

    As well, any mounted forces that did get across would find their withdrawal routes easily blocked, thus acting as a second deterrent.

    In engineering terms, the wall served as an important road by which troops could quickly move from their garrisons to threatened areas. In mountainous regions, that would have been an extremely important force multiplier, allowing troops and horses to move quickly, even at night. Lower walls on the heights would give the road a gentler gradient, making it a better road. On the heights, that was probably the more important role of the wall.

    The second engineering factor is that tall walls need a wider base and, on steep slopes, that would have exposed the base of the wall to slippage and failure.

    In economic terms, lower walls dramatically reduced the effort and material required to build them, especially where heavy material had to hauled up slopes.

    I would be very interested to see what other thoughts people have.


  7. Many of the above responses are on point. In addition to being fortifications, the various sections that make up the great wall were thoroughfares for trade and military reinforcements. Reducing the gradient of the hill increased the functionality of the walls as a road. This could be acheived with little “cost”, as any invaders climbing the hill would have been targets of the fish-in-a-barrel variety.


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