At the height of Western dominance over Islam in the early twentieth century, the European historian Hilaire Belloc (b. 1870) made a remarkably prescient observation that may have seemed exaggerated at the time:
Millions of modern people of the white civilization -- that is, the civilization of Europe and America -- have forgotten all about Islam. They have never come in contact with it. They take for granted that it is decaying, and that, anyway, it is just a foreign religion which will not concern them. It is, as a fact, the most formidable and persistent enemy which our civilization has had, and may at any moment become as large a menace in the future as it has been in the past” (from Belloc's The Great Heresies, emphasis added).
Anyone who doubts that Islam has been “the most formidable and persistent enemy which our civilization has had,” should familiarize themselves with that civilization's long militant history vis-à-vis the West.
According to Islamic history, in 628, Muhammed, the Arabic founder of Islam, called on the Byzantine Emperor, Heraclius -- the symbolic head of Christendom -- to recant Christianity and embrace Islam. The emperor refused, jihad was declared, and the Arabs invaded Christian Syria, defeating the imperial army at the pivotal Battle of Yarmuk in 636 (see my MA thesis on this battle, which one prominent historian described as the world's “most consequential”).
This victory enabled the Muslims to swarm in all directions, so that, less than a century later, they had conquered the greater, older, and richer part of Christendom, including Syria, Egypt, and North Africa.
Their drive into Europe from the east was repeatedly frustrated by the Walls of Constantinople; after the spectacularly failed siege of 717-718, many centuries would pass before any Muslim power thought to capture the imperial city. The Arabs did manage to invade Europe proper and conquered Spain but were stopped at the Battle of Tours in 732 and eventually driven back south of the Pyrenees.
For more than two centuries thereafter, Europe continued to be pummeled by land and sea -- untold thousands of Christians were enslaved and every Mediterranean island sacked -- in the ongoing Muslim quest for booty and slaves, as what historians have dubbed “the Dark Ages” descended on the continent.
The vicissitudes of war ebbed and flowed -- the Eastern Roman Empire (“Byzantium”) made a major comeback against Islam in the tenth century -- though the border largely remained the same. This changed when the Turks, under the leadership of the Seljuk tribe, became the new standard bearers of jihad. They nearly annihilated eastern Anatolia, along with Armenia and Georgia, in the eleventh century and, after the Battle of Manzikert, 1071, overran Asia Minor.
By now, however, Western Europe's military might had so matured that when the Pope called on the knights of Christendom to come to the aid of the Christian East, the First Crusade was born. Western Christians, led by the Franks, marched into the beast's lair, defeated their adversaries in several encounters and managed to establish a firm presence in the Levant, including in Jerusalem, which they recaptured in 1099 -- only to lose it less than one hundred years later, in 1187, after the fateful Battle of Hattin. By 1297, the Crusader presence was eliminated from the Middle East.
But if it failed in the East, the Crusade succeeded in the West. A handful of years after the Muslim invasion and conquest of Spain around 711, fugitive Christians holed in the northern mountains of Asturia began the Reconquista; by 1085 it had proven effective enough to prompt two new Muslim invasions from Africa to counter it. Again, the ebb and flow of war dominated the landscape, but by 1212, at Las Navas de Tolosa, Spain's indigenous Christians gave Islam its death-stroke, so that by 1252 it was confined to Granada at the southernmost tip of Iberia.
Around that same time, a violent but relatively short-lived Mongolian storm overwhelmed much of the east; both Christians (notably Russians) and Muslims were pummeled. A new Turkish dynasty arose from the Seljuk ashes; the Ottomans -- whose identity revolved around the concept of jihad more their predecessors -- renewed Islam's perennial war on Christendom. They managed to enter Eastern Europe, defeated a combined army of Crusaders at Nicopolis in 1396, took much of the Balkans, and crowned their achievement by fulfilling Muhammad's desire of conquering Constantinople -- and enslaving and raping thousands of its inhabitants in ways that ISIS tries to mimic -- in 1453.
But mourning was soon tempered by joy: to the west, Spain finally conquered Granada in 1492, thereby snuffing out Islam as a political power; to the east, the most overlooked chapter of Muslim-Christian conflict was also coming to an end. The Russians, who had lived under distinctly Islamic rule for nearly two centuries, finally cast off the “Tatar Yoke” in 1480.
Even so, the Ottomans continued to be the scourge of Christendom; they continued making inroads into Europe -- reaching but failing to capture Vienna in 1529 -- and sponsored the seaborne jihad originating from North Africa. While the Muslims largely failed to capture new European lands, Barbary pirates and Crimean slavers captured and sold approximately five million Europeans.
In 1683, over 200,000 Ottoman jihadis attempted to take Vienna again. Even though their failure marked the Ottoman Empire's slow decline, Muslim slavers of the so-called Barbary States of North Africa continued to wreak havoc all along the coasts of Europe -- reaching even Iceland. The United States of America's first war -- which it fought before it could even elect its first president -- was against these Islamic slavers. When Thomas Jefferson and John Adams asked Barbary's ambassador why his countrymen were enslaving American sailors, the “ambassador answered us that it was founded on the laws of their Prophet, that it was written in their Koran, that… it was their right and duty to make war upon them [non-Muslims] wherever they could be found, and to make slaves of all they could take as prisoners...”
Finally the Colonial Era came with Europe's triumph over the Barbary States in the early 1800s. By 1900, most of the Muslim world was under European control; by 1924, the more than 600-year-old Ottoman caliphate was abolished -- not by Europeans but Muslim Turks, as the latter sought to emulate the successful ways of the former. Islam was viewed as a spent force and virtually forgotten, until recent times when it reemerged again.
Such has been the true and most “general” history between the Islamic and Western worlds.
The above map should give an idea of how far-reaching and multitentacled the perennial jihad was. The darkest shading represents Western/Christian nations that were permanently conquered by Islam; the lighter or gray shading represents those Western/Christian nations that were temporarily conquered by Islam (sometimes for many centuries, as in Spain, Russia, and the Balkans); stripes represent areas that were raided, often repeatedly, though not necessarily annexed by Islam; the crossed swords mark the sites of the eight most landmark battles between Islam and the West.
From a macrocosmic perspective, the consequences of the historic jihad are even more profound than first appears. After writing, “For almost a thousand years, from the first Moorish landing in Spain  to the second Turkish siege of Vienna , Europe was under constant threat from Islam,” Bernard Lewis elaborates:
All but the easternmost provinces of the Islamic realm had been taken from Christian rulers… North Africa, Egypt, Syria, even Persian-ruled Iraq, had been Christian countries, in which Christianity was older and more deeply rooted than in most of Europe. Their loss was sorely felt and heightened the fear that a similar fate was in store for Europe.
The “loss” of North Africa and the Middle East “was sorely felt” by premodern Europeans because they thought more along religious and civilizational lines than nationalist ones. And before Islam burst onto the scene, most of Europe, North Africa, and the Middle East were part of the same religio-civilizational bloc. As such, Islam did not merely invade and eventually get repulsed from Europe; rather, “Muslim armies conquered three-quarters [or 75 percent] of the Christian world,” to quote historian Thomas Madden.
Thus what is now called “the West” is actually the westernmost remnant of what was a much more extensive civilizational block that Islam permanently severed, thereby altering the course of “Western” history. And once Muslims overran Africa and the Middle East, most of its Christian subjects, to evade fiscal and social oppression and join the winning team, converted to Islam, thereby perpetuating the cycle, as they became the new standard bearers of jihad against their former coreligionists north and west of the Mediterranean.
Such are the rarely noted ironies of history.
Returning to Hilaire Belloc, one can also see how an accurate understanding of true history -- as opposed to an indoctrination in mainstream pseudo-histories -- leads to an accurate prognosis of the future. For Belloc was not only correct about the past but the future as well:
It [Islam] is, as a fact, the most formidable and persistent enemy which our civilization has had, and may at any moment become as large a menace in the future as it has been in the past… The whole spiritual strength of Islam is still present in the masses of Syria and Anatolia, of the East Asian mountains, of Arabia, Egypt and North Africa. The final fruit of this tenacity, the second period of Islamic power, may be delayed -- but I doubt whether it can be permanently postponed (emphasis added).
Note: The historical portion of this article follows the outline of my recent book, Sword and Scimitar, which, in 352 pages copiously documents -- including from little known or previously untranslated primary sources -- the long and bloody history between Islam and the West, in the context of their eight most landmark battles. American Thinker reviews of the book can be read here and here.