The Walls Came a Tumbling Down

Every year or so I visit Hadrian's wall. It was partly built to defend Britannia from the Scotch tribes, partly to control trade and impose taxes. It was an acknowledgement by Hadrian that the long period of imperial growth and expansion was all but over. Rome was big enough and was already somewhat unwieldy. It was also a concession that Roman soldiers, though great, could not conquer everyone; it was an admission of limitation.
President Trump seeks his own wall; if I were an American, I might well support its construction if it assisted with the control of immigration. But, like Hadrian's before him, it will fail in the end, becoming a pile of stones. 
I look forward to the day that Zechariah foresaw. A day in which God's people will neither need nor crave the protection offered by walls:
“And said unto him, Run, speak to this young man, saying, Jerusalem shall be inhabited as towns without walls for the multitude of men and cattle therein” says Zechariah 2.