There has been a lot of blabber lately, from the far right in general and Donald Trump worshipers in particular, about building an enormous wall between Mexico and the United States so as to “stem the invasion of the ‘illegals'”. The Great Wall of China is often named dropped as an example, or rather, THE example of how a wall can be used successfully to maintain the supposed integrity and security of a large nation. You see, there is just one little problem w/ using the example of the Great Wall this way: It didn’t work, or at least not the way people have been led to believe.
China (or more accurately, the areas of China populated and controlled by the Han ethnic and cultural group) was invaded successfully by the Mongols, the Hsi Hsia (Tanguts), the Tibetans, and the Manchu. The wall, or rather serious of walls (made variously of stone, wood, and earth at different places along its length) and border forts linked by trade and communication networks and manned by pickets and conscripted militias along with the Imperial military, was basically a giant propaganda tool and a way to martial large amounts of labor resources and maintain control of frontier regions, protect against bandits, and control import/export trade. So, long story short, walls don’t work as ways of keeping large amounts of people out of large nations and they are almost never effective at “controlling” the flow of migrants. People are like water; they will always find a way through even the most tough and powerful looking barrier.
Also (talking to you here Mr. Trump and your supporters) China never made the other nations that were meant to be kept out by the wall pay for the wall. China tried the whole bravado/middle finger technique against the Mongols, and, well, the Mongols invaded China, killed 20 Million people, burned many of its largest cities to the ground, and ruled it as conquerors for 150 years. So there’s that. Unless we are willing to post tens of thousands (perhaps hundreds of thousands) of armed to the teeth soldiers on and around the 2000 mile border permanently (like the Israelis in Palestine, the Soviets in East Germany and North & South Korea on the DMZ) said wall is not going to solve the “problem” of unregulated immigration into the United States from Mexico and Central America. And even THEN, as the China examples shows, it wouldn’t work. Only a “giant loser” would think otherwise.