If this shutdown had proven anything it has proved that Trump has a grasp of time longer than he's been alive which he frequently displays with his informative lectures on the 'medieval' technology of walls and his amazement at their ability to best the ancient technology of wheels. Now we've heard from nearly every corner of educated American society ranging from artists to politicians to even architects just how wrong this wall is and the various ways it isn't going to work. However in this discussion there is one important group that has not yet weighed in on the wall issue and that group is the historians who can give us an answer supported by the weight of history on whether walls work. Let us take a journey through time and examine some of the most famous walls ever built.

We'll start with Hadrian's Wall in what is now England as it is the oldest wall on this list. Roman emperor Hadrian built the wall partly to defend the Roman province of Britain from marauding bands of Picts and other barbarians coming out of the north and partly to serve as an expression of roman power. At both of these purposes the wall ultimately proved futile as upon the next emperors ascension the wall was abandoned for a new one further north. Additionally the wall proved difficult to maintain and garrison and was eventually abandoned as Roman control over Britain gradually declined.

We move on nest to what are probably the most successful set of walls in history the Theodosian Walls of Constantinople in what is now the European part of Turkey. The walls were built by the Byzantine emperors to protect their capitol and for over 900 years they managed to successfully repeal attacking armies from dozens of rival nations. Now before you go off thinking that this proves that walls indeed can work consider for a moment the current name of the city as a hint to their ultimate fate. The fact that the city is Istanbul and not Constantinople shows just how well walls can keep out an enemy, especially when that enemy has such modern technology as cannon. Good thing nobody else knows the secrets of gunpowder else the rest of the world's wall should tremble in fear, right?

Our next wall is probably the most famous wall in the world and the wall that Trump most commonly cites as his inspiration, the Great Wall of China. The Great Wall is not one single wall but a series of walls and other fortification built by various Chinese dynasties to keep out invaders particularly from the Mongol Steppes. The Great Wall however was ultimately unsuccessful in this goal as more than one Chinese dynasty originated from invaders who manages to breach the great wall, not the least of witch were the Mongols themselves.

Now you might be thinking that in this modern era of science where we possess such technologies as airplanes and high explosives that walls would be obsolete and vanish from the world and you would be partly correct. The walls of today are less solid stone edifices towering above you but rather a metaphor for an elaborate system of defensive works typically made of concrete. Take for example the Nazi's Atlantic Wall built to defend their conquests in Western Europe from Allied invasion. The wall stretched from the Spanish border up to the Arctic Circle and consisted of thousands of pillboxes, bunkers, gun emplacements, minefields, and various other nasty surprises for an invasion. The Wall was probably one of the largest and most sophisticated defensive systems ever created by human hands and it took only a day to breach it. Once the Allies secured a foothold on D-Day the Wall was rendered useless and became little more that a sideshow in the liberation of Europe and a crumbling monument to Nazi vanity after that.

Our final wall is the most recent wall on this list and the one I think that most captures the spirit of what Trump is trying to do, the Berlin Wall. The Berlin wall was built in 1961 by the East German government to prevent citizens from fleeing to the west trough the Allied occupied section of Berlin. The wall was a collection of concrete barriers, guard towers, and open spaces that became know as the 'death strip'. Over 150 people died trying to make it over the wall and yet despite its lethality over 5,000 people still manages to defect with tens of thousands more still making the attempt anyway.

From reviewing this collection of notable walls there are a few things we can learn. The first is that no wall is impenetrable. If a group of people is determined enough and resourceful enough they will find a way through the wall no matter how big or deadly you make it. The second is that when walls do work it is because they are one part of a much larger system rather than a thing unto themselves. The Theodosian Walls succeeded for as long as they did because they were part of a much larger imperial defense system supported by various armies, navies, and civil servants. This is something that I fear Trump does not realize, a southern boarder wall is not going to be just a wall but an entire system in itself with a veritable army needed to patrol it and maintain it. Frankly it is entirely possible that more people will be needed to garrison the thing than it will ever stop crossing the boarder.

The wall is likely to be a money pit to rival all other money pits, as it will require an ever-greater quantity of resources to maintain for almost non-existent returns. What's more it is very likely that whoever the president after Trump is will simply order the thing halted and put the money into other more productive projects either destroying what's already been built or leaving it to crumble as another monument to oppression and authoritarian vanity. No matter what way you look at it the wall flies in the face of nearly every historical lesson about successful wall usage at to be used as a cheap propaganda tool by an oafish president.