Of the many national debates over policies proposed by President Trump, few have generated more vitriol than his pledge to build a great wall on the southern border. While some on the left (and even the right) have argued about the cost or even the need, the most shocking arguments came from liberals and even some libertarians who flatly claimed that the wall won’t work. This argument was summed up earlier this year by David Bier at Reason Magazine in his piece, “Why the Wall Won’t Work.”

David goes into a number of debate points about the high cost, the lack of political will and even the unknown efficacy of such a barrier. The first two are obviously worth discussing, but at what point did we decide that walls don’t keep people out? (Or even in?) Allow me to offer you a real world example which might cause you to rethink that position. There’s a news item which was picked up over at Breitbart but originated in several European sources. It has to do with Viktor Orban, the Prime Minister of Hungary, and the double fence he put up along the border of his country with Serbia.

That was two years ago. And what’s happened since? What was once a flood of people crossing into Europe has now shut down to virtually nothing.

Speaking on the second anniversary of the government’s move to seal Hungary’s border with Serbia — which is also an external border for the European Union — Prime Minister Viktor Orbán’s Chief Security Advisor György Bakondi announced that the fences have caused illegal immigration to collapse from 391,000 in 2015, to 18,236 in 2016, to just 1,184 in 2017. “The system of technical barriers is the key to the success of border security, and without it, it would be impossible to stop the mass arrival of immigrants”, the security chief explained. Hungary had to respond rapidly to the migrant influx which burst upon Europe after Germany’s Angela Merkel announced there was “no limit” on the number of asylum seekers her own country would accept, so its frontiers are defended by twin fences peppered with watchtowers and patrolled by thousands of newly recruited border guards rather than a solid wall — which would have taken longer to construct.

The math here should be a bit too much for any but the most willfully blind to ignore. In 2015 there were an estimated 390,000 illegal border crossings. Thus far this year the number is barely over one thousand. That’s not just impressive… it’s staggering.

Of course, we have to keep in mind the nature of that country and the leader who made this happen to understand the full phenomenon. Viktor Orban is the guy who was told by the European Union that he couldn’t put the fence up in the first place. He proceeded to build it anyway, doubled it, and then sent a bill for half the cost to the EU. (I don’t think he’s really expecting to get a check for it.) Then, when Angela Merkel announced that Hungary would have to stop defying the edicts of Brussels, he thanked her for her input and then basically told her to go pound sand.

This was never a question of whether or not a wall (or in this case, some other effective form of barrier) could work. Walls work all over the place, otherwise we wouldn’t have been building them for the entire recorded history of man. But in order for such a barrier to exist and do its job you have to have the political will to make it happen and to put the required resources into manning and maintaining it. If you can’t manage those portions of the formula, obviously the wall can’t work.

But as Viktor Orban has demonstrated in stunning fashion, once you get your act together and actually do it, it works. This isn’t to say that we don’t face more challenges than Hungary, having a much larger border and more variable terrain to cover. But that’s not what’s stopping us at the moment. The real reason a wall isn’t working for us on the southern border is Congress, not physics or engineering questions.