What It Would Take for Donald Trump to Build the Great Wall of America

Pay any attention to the news lately, and you could be forgiven for forgetting that Mexico is one of our strongest allies in the world. It's the third largest trading partner of the US after Canada and China. When ranked in order, more American tourists flock to Mexico every year than the next four countries on the list combined.

All that being said, top presidential candidate Donald Trump wants an actual wall along the US-Mexican border, and he wants Mexico to pay for it. GOP hopeful Ben Carson would supplement that with armed drones. Scott Walker also thinks that would be a feasible idea.

The United States's southern border extends about 1,954 miles running from California to Texas. There are four states on the American side, and six on the Mexican side. It runs through two major deserts, the Sonoran and the Chihuahuan, the second of which is the largest desert in North America. The trek across the border is dangerous; hundreds die attempting it every year, though those deaths are declining as immigration from Mexico in general declines.

The only precedent for a border security project this large in the modern world would be the Maginot Line from WW2, a series of connected fortifications and supply lines with which the French quite unsuccessfully tried to protect themselves from Germany's lightning fast military advance. The Germans simply stepped around it and invaded through Belgium. Otherwise, the best comparison might be a couple of thousands of years older: the 5,500 mile long Great Wall of China.

The seemingly sudden interest in building a physical barrier along nearly 2,000 miles of hostile desert terrain raises interesting questions, some of them political, and some of them technical. We're not at war with Mexico. But the added focus on the border we share might point us to warfare technology's next front.

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Wall building in the modern era is a relatively new phenomenon, said Reece Jones, a professor of geology at the University of Hawaii and author of Border Walls: Security and the War on Terror in the United States, India, and Israel.

"At the end of World War II, there were less than five border walls anywhere in the world and then in the period from 1945 through the fall of the Berlin Wall in 1989, there were something like ten built during that entire period," Jones told Motherboard.

Since the 1990s, wall building has accelerated. Today roughly 60 countries have walls on their borders, and three quarters of those were built in the last 25 years, Jones said.

That's counterintuitive given that modern warfare killed the concept of the wall. Unlike the days when the Great Wall protected the Ming Dynasty's empire from Mongol raiders, war no longer refers to armies of men clashing. If the consideration is armed conflict, a wall is as useless as the proverbial knife in a gunfight.

Most of these walls don't serve a military purpose, Jones said.

"From research that I've done with another scholar what we found is that there's a pretty strong correlation between borders and countries that have a sharp wealth disparity across them," he said. "All the military [use] of the walls is justified using the language of terrorism and the duress of people coming in from the outside. It seems like the underlying issue in most cases is an economic one."

Still, the hypothetical US-Mexico wall, even though it's aimed at stopping illegal immigration and protecting the local economy, would likely have to be built by the military—the only organization capable of pulling off such an ambitious project. But it will have to be more than a physical barrier.

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What makes a good wall? The ratio of manpower to wall length, for example, seems like a good barometer of safety. An outside prison wall 100 feet long with 10 guards to patrol would be pretty secure, for example.

There are currently 20,824 Border Patrol Agents, the personnel responsible for actually patrolling the border and securing it. They're not military, but that distinction means little when you consider that they're heavily armed agents of the State who have to pass pretty extensive physical training. So 20,824 agents patrolling a wall 1,954 miles is almost exactly a 10 to 1 ratio, just like that hypothetical prison wall. The problem? Those 20,824 aren't just responsible for the southern border with Mexico, they also patrol the northern border with Canada, which just happens to be the longest international border in the world. (Scott Walker wants a wall there too, by the way.)

That's part of the reason why plans for a Great Wall should now focus on deploying new technology to fortify the US against newcomers. A high tech wall—say, one equipped with autonomous robots, outfitted for surveillance and defense—could deter immigrants and even bolster the line of defense in a modern war.

In 2005, the Department of Homeland Security conceived the Secure Border Initiative Network (SBInet), a radical plan to line the southern border with camera and and sensor equipped watch towers.

The program was a resounding disappointment, costing almost $1 billion to cover just 53 miles. A Government Accountability Office report found the DHS completely unequipped and unprepared to plan and execute such a massive project. The report found that DHS officials did "not effectively managed and overseen its SBInet prime contractor, thus resulting in costly rework and contributing to SBInet's well-chronicled history of not delivering promised capabilities and benefits on time and within budget."

Homeland Security doesn't have nearly as long a history dealing with contractors on huge projects as say, the Department of Defense, which may have accounted for some of the logistical failings. But if at first you don't succeed, recycle old ideas and attempt again.

The DHS has enlisted the help of Israeli defense contractors to once again erect a "virtual wall" of cameras and other monitoring equipment along a much smaller part of the Arizona portion of the border. A technical, if not literal, successor to SBInet. The firm is taking lessons it's learned along the West Bank to help America watch its own yard. Cameras, drones, and conventional air support; in conjunction these make up our "wall."

Right now, about 652 miles of the border is actually protected by a physical fence, thanks to the Secure Fence Act of 2006. These efforts, in addition to the aerial support pledged (including nine $12,000 an hour drones Border Patrol has at its disposal) may be as good as it can get along the southern border until the government decides to spend billions to build Trump's Great Wall.

"Walls in the mind often stand longer than those built of concrete," the German Chancellor Willy Brandt once said. A Great American Wall is probably a fantasy, but fantasies of security have their place, erected right between us and them.

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