[Below are a few pictures of the Vatican's walls - just to add some much needed perspective on the situation]
Context: A couple of years after Islamic prophet Muhammad died in 632, his followers erupted out of Arabia and conquered the surrounding lands of non-Muslims in the name of Islamic jihad. In a few decades, they had conquered two-thirds of what was in the 7 century Christendom. They took all of the Middle East, North Africa, and Spain, until they were finally stopped at Tours in central France (732). By the late 9 century, jihadi incursions had transformed the Mediterranean into a Muslim lake; the major islands—Sicily, Crete, Rhodes, Malta, Cyprus—were conquered, and the European coast was habitually raided for booty and slaves.
It was in this context that, in 846, Muslim fleets from North Africa landed near Rome. Unable to breach the walls of the Eternal City, they sacked and despoiled the surrounding countryside, including—to the consternation of Christendom—the venerated and centuries-old basilicas of St. Peter and St. Paul. The Muslim invaders intentionally desecrated the tombs of the revered apostles and stripped them of their treasures, including a large golden cross. Pope Leo IV (847-855) responded by building large walls and fortifications along the right bank of the Tiber to protect the sacred sites from further Muslim raids. Completed by 852, the walls were in most places 40 feet high and 12 feet thick.
Today, many Muslims, not just of the ISIS-variety, continue to boast that Islam will conquer Rome, the only of five apostolic sees—the other four being Antioch, Alexandria, Jerusalem, and Constantinople—never to have been subjugated by jihad. Similarly, Muslims all throughout Europe continue exhibiting the same hostility and contempt for all things and persons non-Islamic, whether by going on church vandalizing sprees and breaking crosses, or by treating “infidel” women as theirs by right for sex and rape.
In short, Pope Leo’s walls prove Pope Francis wrong on both counts: yes, walls are sometimes necessary to preserve civilization; and yes, Islam does promote violence and intolerance for the other—far more than any other religion. This fact is easily discerned by examining the past and present words and deeds of Muslims, all of which evince a remarkable and unwavering continuity of violence for “infidels.”
More ironically, had it not been for Pope Leo’s walls—and so many other Christian walls, such as Constantinople’s, which kept Islam out of Europe for centuries, and Vienna’s, which stopped a full-blown jihad as recent as 1683—there might not be a pope today to pontificate about how terrible walls are and how misunderstood Islam is. And when Francis accuses those who want to protect their people by building walls of not being Christian, as he did of Trump, he essentially accuses his betters—men like Pope Leo IV, who did so much to protect and preserve Christendom at a time when Islam seemed to be swallowing up the world—of being no Christians at all.