Before the rise of Islam, the region we call the Middle East was predominately Christian. There were Zoroastrians in Persia, polytheists in Arabia, and Jews in Palestine, but most of the people in what we now call Iraq, Syria, Jordan, and Egypt were Christian. The sacred places in Christianity - where Christ was born, lived, and died - are in that region. Inspired by Islam's call to jihad, Muhammad's armies conquered Jerusalem and the entire Middle East, then pushed south into Africa, east into Asia, and north into Europe. They conquered parts of Italy and most of Spain,invaded the Balkans, and were preparing for a final incursion that would bring all of Europe under the rule of Islam. So serious was the Islamic threat that Edward Gibbon speculated that if the West had not fought back, "perhaps the Koran would now be taught in the schools of Oxford, and her pulpits might demonstrate to a circumcised people the sanctity and truth of the Revelation of Mahomet."
Specifically, Syria and Persia were home to thriving Christian communities, who lived in peace with the Zoroastrians, and who produced a culture flourishing with its own art and literature. Ephrem the Syrian, for example, who died around 373 A.D., wrote a large collection of poems. The areas around Persia and Syria were the heartland of the Nestorian church - remember that 'Persia' is what is today called 'Iran'!
But the Christian communities which had peacefully existed for centuries - the Copts in Egypt, the churches in India, Afghanistan, and what is now Pakistan - were suddenly subjected to the murderous rage of invading armies. They were killed by the thousands; those who survived were oppressed and maintained faith only by means of the strictest secrecy. Throughout Africa, the native population was deprived of its own religious traditions as Islam was imposed upon it. In the early 700's, Spain was invaded by Muslim armies coming from northwest Africa.
In Spain, the Islamic invaders destroyed churches and synagogues, oppressing the Christians and Jews who'd lived together peaceably for centuries. The caliphs - Muslim rulers over subjugated nations - forbade the reconstruction of the destroyed churches and synagogues, or the building of new ones. The invaders called this "the golden era of tolerance in Spain," but the Jews and Christians there were mercilessly persecuted.
Having taken most of Spain - a small section of northwestern Spain remained free by means of valiant resistance - the Muslim attackers moved on France. Most famously by Charles Martel in the 730's A.D., but also by other leaders at other times, the French - the Gauls under the Frankish leadership of Merovingians and Carolingians - repelled the ambitious invaders.
From north-central Africa, other Islamic armies invaded, first Sicily, then the southern end of Italy in the 800's A.D. Southern Italy suffered under the harsh rule of the Muslims, who several times attempted to pillage their way north to central Europe.
Starting from Arabia, and moving in nearly every direction on the compass, Islamic armies struck terror into a large part of the world, killing tens of thousands, and destroying peaceful religious communities.
More than two hundred years after Islamic armies conquered the Middle East and forced their way into Europe, the Christians finally did strike back.
These counterattacks - remember that "the best defense is a good offense" - were an attempt to get at the source of the continued invasions. Rather than meet the invaders as they entered European countries, the Europeans hoped to get at the military base to prevent the Islamic invasions from starting in the first place. These measures, starting in the 1090's A.D., are listed as "the Crusades" in the history books, but that word was not used at the time by the Europeans or by the Muslims. Sadly, the Europeans were able to gain at most only a brief reprieve from Islamic attacks, for soon after the Crusades ended, Islamic armies were again on the march against other nations. Europe's counterattacks
were a belated, clumsy, and defensive reaction against a much longer, more relentless, and more successful Muslim assault against Christendom.
The Crusades were simply too small to be significant, compared to
the Islamic jihad to which the Crusades were a response.
Today, art historians mourn the absence of good examples of early wooden-roofed basilicas in Spain. Priceless architectural monuments were destroyed by the Islamic armies which ravaged Spain. The sacred art of the Christian communities which flourished in Syria, Arabia, Egypt, Persia and other Asian regions is largely lost to the scholars of the world's cultures.