As this article from The Imaginative Conservative, Belloc’s warning was prophetic.

An excerpt.

1938, The world is on the threshold of the most devastating war in history, and totalitarianism is everywhere on the march. The Anschluss takes place in February. Later, in October, Germany annexes Sudetenland. In November, Kristallnacht. Beria becomes head of the Soviet secret police. The infamous Rape of Nanking culminates that year, and the great purge is finally winding down in Russia. Japan passes the National General Mobilization Law, focusing the entire Japanese economy on military readiness. The fascist takeover of Spain is nearing completion, and the Pact of Steel between Germany and Italy is only a year away, as is the formal start of the World War. Hitler is Time Magazine’s Man of the Year, edging out Stalin who wins the title in 1939.

That same year, a now-obscure Franco-British author saw things differently. In what certainly seemed at the time a bizarre, clueless historical non-sequitur, Hilaire Belloc publishes this peculiar warning: “The future always comes as surprise… but I for my part cannot but believe that a main unexpected thing of the future is the return of Islam.” He elaborates: “It has always seemed to me possible, and even probable, that there would be a resurrection of Islam and that our sons or our grandsons would see the renewal of that tremendous struggle between the Christian culture and what has been for more than a thousand years its greatest opponent.” With great prescience, he adds: “There is no reason why its recent inferiority… should continue indefinitely. Even a slight accession of material power would make the further control of Islam by an alien culture difficult. A little more and there will cease that which our time has taken for granted, the physical domination of Islam by the disintegrated Christendom we know.”

At the time Belloc published these and many more warnings in his books, The Crusades: the World’s Debate (1937) and The Great Heresies (1938), the historical lands of Islam had been carved up by the European powers and seemed powerless to ever rise again. It was obvious to all the “experts” of that time that it was fascism and communism, and other more modern manifestations of totalitarianism, that imperiled freedom and democracy. Belloc’s clarion call was seen as so absurd and out of touch with current events that it went largely unnoticed for many decades. But Belloc sensed that the rise of fascism and communism were passing fads—that the soulless ideologies of Marxism’s class warfare and the racist, nationalist rants of the fascists could not long capture either the imagination nor the soul of Western civilization. For Belloc, it was Islam, long quieted under the boot of European imperialism and seething under colonial misrule, that remained the true, enduring, and implacable threat to Western values and culture.

I do not share Belloc’s almost Manichean view of the struggle between what he termed Christendom and the Islamic world. Indeed, most of us would reject his use of the term Christendom, and it is hard to accept the urgency of his call to restore a unified Christendom to counter the “perpetual” Islamic threat. In truth, some of his views of Catholicism neatly dovetail with the worldview of too many Muslims, who disdain the secular state and view religion as a way of life that takes precedence over all other loyalties, whether to family, friends, or one’s country. But his insights into the internal dynamics of Islam and his rightful fear that a religion as vibrant, virtuous, and sometimes virulent as Islam is a serious challenge to our modern understanding of country and community warrant consideration.