One day last week, I spent my lunch break in a tree-lined parking lot, eating a salad in my car and listening to the audiobook of The Secret History of the Mongol Queens. That day’s chapter was about the political, military, and environmental factors that went into the building of the Great Wall of China. That Mandukhai Khatun (Queen Mandukhai the Wise to us English-speaking peons) was a credit to her ancestor Ghengis Khan, as almost none of his other descendants were. Also, Commander Wang Yue of the Ming Dynasty was quite the poet in his military reports.

Here’s the gist. The Mongols were in the habit of raiding the fertile pastureland of the Yellow River (also called the Black, Green, or Red River, depending on which people group you ask). The Mongols had once held this territory and wanted it back, in part to provide good grassland for their horses. But it wasn’t grassland at the time; it was farmland, because the Chinese were using that area to feed their empire. The Chinese had to trade with the Mongols for horses because they were farming the pastureland and prices rose. The Chinese military leaders were incapable of defending the border towns and spent most of their time either waiting for news of an attack or futilely chasing after the Mongols, always one town behind.

So, once a favorable cost-benefit analysis was presented to the Ming court, a Chinese courtesan basically said, “Yeah, this is definitely the best option. It’s much more civilized than posting more soldiers up there…or feeding them adequately, or paying them adequately, or training them at all.” This statement was followed with a chorus of, “We’re incredibly civilized! We’re so super civilized, you guys.” (The Ming built entire tribute system on encouraging others to become what the Ming considered to be “civilized,” which just meant being as much like the Ming as possible.)

“A wall is far more humane than killing the poor barbarians who we can never seem to catch, let alone defend against,” reasoned some courtesan. “The wall will keep our farmer-soldiers from deserting us and the Mongols from raiding us. It’s brilliant! So simple.”

And that kind of double-speak to justify a wall sounds rather familiar, in tone if not in words. And walls are such good ideas! Walls solve everything. There’s no problem a big, strong wall can’t fix. Just ask the Chinese, whose wall may or may not have directly contributed to the Ming dynasty’s fall. (No, really! Historians and economists disagree about how much the wall had to do with the empire’s fall. This wasn’t my area of emphasis in my history degree, either, so I’m not going to weigh in. However, most historians agree that the wall served as a symbol of the dynasty’s downfall, and still does today.)

That’s basically what I remember about the Great Wall from my school days. I learned that the wall was built in parts first, then connected, and lots of people died in the process. I learned the great wall isn’t straight because the Chinese believed that evil spirits follow straight lines, and I learned that the wall didn’t really work.

Now, to be fair, the region did stabilize economically after the completion of the wall and a failed Mongol raid in 1482, but the stability likely had as much to do with the legacy of Mandukhai Khatun’s rule (remember, she’s the really cool Mongol queen directly descended from Ghengis Khan) as it did the wall. In terms of repelling invasions, though, the wall did precious little in the 130 years between completion and the dynasty’s fall.

So, to anyone wanting a new wall, literally or figuratively, let me point out a few things that the Ming didn’t know when they built theirs.

1. Racism hurts everyone. That includes you, no matter what ethnicity you are. You may not feel the effects in the short-term (though Chinese and Mongol people died because of that wall), but you better believe that future generations are going to shake their heads in frustrated disgust at you. And no one loves to tear things down more than the young, jaded idealists who grew up in a big wall’s shadow. (Berlin, anyone?)

2. There’s no such thing as a simple solution. Not in border disputes, not in economics, not in policy, not in life. The complex problems that people build walls to try to solve will not be solved once a wall is complete. Rather, the problems will morph, affecting new aspects of society and causing entirely new problems, or they will swell until the wall can no longer hold back the flood.

3. Avoid building symbols of power. They are too fragile to maintain and protect, but become too important psychologically to let fall. If the symbol goes, so does the illusion of your strength. You’ll invest immeasurable amounts of time, energy, money, and other resources defending your symbol, and you’ll have to continue long after it’s outlasted its original usefulness. Or long after you realize it never fulfilled its original purpose. You won’t be able to defend it from others or get rid of it yourself (ie, US sanctions against Cuba, maintained until after Fidel Castro’s death).

Clearly, I’m not outlining my own complex solutions to the world’s ills. But I am cautioning us to really think through the literal and figurative walls being built in US foreign policy.