As an operative I took advantage of my interest in Anthropology. At the time my studies were just a hobby, but more times than not I fund the success of the prime objective was only achieved by making the enemy believe that I belonged there.
Psychology has its uses but when you know nothing about the person you are dealing with you must really on your knowledge of the current cultural landscape of the group you are dealing with.
From a distance I could make observations and even learn enough of the language to be able to pass through what ever security they might have. Before the mission would go hot I would even get to know the guards.
In fact I even bought gifts for one of the guards families a week before Christmas. But to do that I had to get to know him well enough to understand that he secretly converted to Christianity a few months before.
If you are going to put up walls like Trump talked about, you must also understand that walls and fences don’t add to security if the enemy wants in. For me it only takes three or four hours to be fluent in a Easter language and 30 minutes for a Latan based language. If the Enemy puts up walls and fances you just walk in through the front gate.
You make friends with them and start conversations with the guards. After a while they forget that they didn’t check to see if you belong there.
My point is a warning to our new President. The more secured you think you are making something, the bigger the cracks are in the armor.