what does history say about the effectiveness of border walls for national security?

GMartin used Ask the Experts™
Hello and Good Afternoon Everyone,

           With so much division being stirred up because of a proposed U.S. / Mexico border wall, I have to wonder the following:  What has history said about the effectiveness of a wall like back in Roman times, The Great Wall of China, etc. ?

            Any historical perspective given to this current state of affairs will be greatly appreciated.

            Thank you

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The Berlin Wall did not stop people from escaping from East Germany into Berlin.
The majority of illegal immigration into the US is by people that arrived with a valid Visa and decided not to go home.
A fixed wall doesn't stop people from going UNDER or Around it. Unless you want the great wall of USA around the entire country.  The great wall of china did not stop the Manchu's or the Mongols from invading https://en.wikipedia.org/wiki/Great_Wall_of_China  The Maginot line did not stop the Germans from invading France.  The Atlantic Wall did not stop the Allies invasion

The wall if built will then mean the use of eminent domain to take land from people that own the land where they want to place the wall. Farmers will have to some way or another use another source of water other than the Rio Grande.

Please read this well thought out article on the US Border Wall https://www.cato.org/publications/commentary/why-wall-wont-work
Yes, and the difference between the Berlin wall and the proposed mexico/USA one is that the Soviets built the wall to prevent their people from escaping, not coming in.

An impenetrable wall would require border guards at very close intervals with the means to stop "invaders" by force, i.e. guns.  It would also impede migration of land animals.  Anything other than impenetrable would be useless for the proposed purpose.

I gather that Mr. Trump compared his idea to that of the Vatican City in Rome and Mark Zuckerburg's private home.  There are huge differences, for example here's what you get on Google if you type in "Vatican City":  "Vatican City | Avoid the Queues & Book Now | TripAdvisor.co.uk‎".  That's not really an impenetrable fortress that repels people, is it?  Neither is a private home surrounded by high walls for privacy reasons.

As David mentioned, how on earth (or actually on water) do you build a wall down the middle of the Rio Grande River that forms part of the virtual border.

You mentioned Roman walls.  There are two examples of walls built by the Romans during their occupation of Britain, namely Hadrian's wall (https://en.wikipedia.org/wiki/Hadrian%27s_Wall) and The Antonine Wall near where I live (https://en.wikipedia.org/wiki/Antonine_Wall).  They are both obviously in ruins now, but the remains of Hadrian's Wall lies entirely within what is now England but in some ways parallels the "border" between England and Scotland, while The Antonine Wall is half way up Scotland roughly where the wild Northern Scots would have come down to.

Their purposes are not known with absolute certainty, but it is thought that the Antonine Wall was an expression of Roman power to dissuade the Scots from the land of Caledonia (North of the wall) from pushing further South and acquiring the Roman lands that were called Brittania, whereas Hadrian's Wall was not only a show of strength and dominance, but was used as customs control points to collect taxes.  Although Hadrian's Wall was 16 to 20 feet high and had Roman garrisons at intervals along its length, it also had numerous "gates" through which people passed both ways on a daily basis where the only impediment to their migrations was tax collection.

Neither of these walls were economically viable and the Romans surely knew that they would not prevent migration of people between the separated areas.  In the same way that the blustering fool of a narcissistic president loves to demonstrate his perceived superiority, the Romans relied on these facades and shows of strength to intimidate people.  The difference was that the Roman empire was exceedingly rich, had many thousands of canon-fodder soldiers, and also had slaves to build, man, and maintain their walls.
I'm not a fan of what is being proposed by the President, but I don't think that the Great Wall of China or Roman walls are fair comparisons, whether or not they worked.  The methods used to defend the walls and to breach them are very different between now and then.

Though the Berlin Wall wasn't 100% effective, it was very close.  It also took a lot of people and money to support it.

My big concern with discussion of the Wall (and most of the other hot political topics these days) is that we're getting lost in some of the specifics and avoiding discussions and decisions about the larger policy issues.  I think we need to start with reaching some sort of consensus on what it is we want in the way of immigration and then work toward reasonable ways of accomplishing it.  That discussion seems to be avoided by both sides.
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>>> "I'm not a fan of what is being proposed by the President, but I don't think that the Great Wall of China or Roman walls are fair comparisons" <<<

Correct, but George Martin asked about those two historical things and Trump is the very one that made such ridiculous comparisons with his proposed wall, in particular the Vatican City but also about Barack Obama's walled home:

"When they say the wall is immoral, well then you better - got to do something about the Vatican, because the Vatican has the biggest wall of them all".

"There's a reason why politicians and wealthy people build walls around their houses and their compounds. President Obama recently built a wall around his compound".

I can't find a quote of his alleged comparison with Mark Zuckerberg's home.  It is probably based on an old tweet by Trump after Zuckerberg criticised his idea of a wall.

>>> "The methods used to defend the walls and to breach them are very different between now and then." <<<

Not really.  Take the example of The Trojan Horse, where (after 10 years of trying to take over the city of Troy) the Greeks constructed a huge wooden horse and hid soldiers inside. The Greeks pretended to sail away and the Trojans pulled the horse into their city as a victory trophy. The Greek soldiers crept out of the horse and opened the gates for the rest of the Greek army which entered and destroyed the city of Troy.

That isn't really too different in general principle from migrants stowing away in shipping containers and commercial vehicles to cross borders illegally.  People have used ladders to scale walls of fortifications and barrier walls for centuries.  Although CCTV and radio communication are modern technologies, in ancient times the Romans and other civilisations simply built their observation/sentry posts close enough together that they could see exposed sections of walls and could raise alerts by quite elaborate signalling.  In more recent history reflective objects were used to flash codes.  Semaphore flags are still used by the modern navy, just as they were on The Great Wall of China.  Nothing much has really changed when talking about evading barricades and sentry points other than the fact that a tighter barricade only encourages unscupulous people to cash in on more highly organised people smuggling.

>>> "Though the Berlin Wall wasn't 100% effective, it was very close." <<<

Yes, in keeping people INSIDE the country whose military were guarding the wall and fences by shooting people who tried to escape over it to West Berlin.  That would equate to Mexico building its own wall and shooting its own migrants who tried to breach it and run away INTO America - NOT America supposedly defending itself from rapists and drug dealers entering from Mexico.

Where you have a country that is shrouded in secrecy and has a tyrannical regime you tend to have lots of people being secretly shot while trying to escape from its clutches and people only discover the full extent of that tyranny after the walls are torn down.  How on earth would America, in the public eye, choose to pursue and apprehend migrants who would/will undoubtedly manage to circumvent "the wall" and make a run for it just as they do at the moment over the border?  Shoot them?  Set dogs onto them?  Lethal force is hardly justified, but nothing would surprise me about Trump's thought processes.


Hi Everyone,

       Thank you for your thorough and comprehensive feedback.  I found myself reading and even re-reading the comments given here.  I can honestly say that I have learned a great deal from this post.  

I think there's a bigger question with regard to the wall proposed by the President.  What exactly is it intended to prevent?  As I understand it, immigration from the south is declining, other than families from south of Mexico.  Drugs generally come through existing checkpoints so the wall would not change any of that.  The majority of people here illegally arrived legally and overstayed their visas.

There are plenty of stories about vicious crimes committed by people not here legally.  I never seem to find any claims about how they got here.  If they came through the existing checkpoints, a wall isn't going to change the problem.  If they came through elsewhere, the wall might be able to help.  Shouldn't we know these facts before spending $5-20B?

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