It won’t surprise you that, in recent years, for instance, the world has seen an acceleration in the construction of physical barriers, of fences and walls running between nations and defining and in and out. Roy Hassner and Jason Wittenberg, two American political scientists, scored out the pace of global wall building and found a sharp acceleration: In fact, of 51 national enclosures built since the end of World War Two - the Berlin Wall being the most famous example - more than half were constructed in a rush of self-protection between 2000 and 201426, And more are coming: Hungary, Kenya, Algeria and India now posthole their borders in initial exploration of what might be built. There’s a frantic urgency to some of this. The Spanish government, for instance, raised a ten-foot high, razor and camera topped fence around their Saharan footholds in 1998 - the enclosed land was controlled by Madrid, so it was technically “Europe,” which made an irresistible target for would- be migrants. The fence wasn’t enough to stop the flows. So they built a second one to run around the first in 2001. Then, in 2005, thousands of desperate Africans launched a coordinated charge against. A couple of dozen migrants died in the attempt; a thousand made it through. The Spanish responded with a third line of fence, this one 20 feet high, electic, camera-watched. This pattern of ever more stacked defense is repeated everywhere. The walls, fences and trenches of the modern world seem to be getting longer, more ambitions, and better defended with each passing year, Hassner and Wittenberg concluded. Unlike traditional lines of defense, the Maginot Line or the Great Wall of China for instance, the aim of 215t century barriers in places like Israel or the US or Spanish Morocco have been less to stop a rolling armor blitzkreig than to slow the insidious movement of smugglers and spies and criminals, or the hopeful dashes of fleeing refugees. There’s an affective and - to those on the inside -