The First Crusade (1096-1099) spawned horrors the likes of which none of the crusaders had ever experienced. And they were horrors of their own making. Of the massacre in Jerusalem, a contemporary observed, "The knights could hardly bear it, working as executioners and breathing out clouds of hot blood."
Particularly during the sieges of Antioch, Ma'arra, and Jerusalem, whose populations were brutally massacred, the First Crusaders themselves believed that they had exceeded all the norms of medieval warfare, and the evidence supports them. Even the most brutal sieges of the day ended in mass enslavement of city populations, not in mass murder.
The observation is simple enough, but for modern, Western audiences, it inevitably raises a question (one I have gotten several times on these very pages, in fact): What about Muslim atrocities? Weren't the Muslims just as bad? After all, the Holy Land had once been thoroughly Christianized. What became of those Christians? Surely the Muslim conquests were just as brutal as the crusades?
The short answer is, "No." But, let me explain:
The spread of Islam in the seventh and eighth centuries C.E. is one of the most astonishing events in history. What started in 622 C.E. (year 1 of the Muslim calendar) as an obscure desert religion on the Arabian Peninsula, 150 years later had established its rule over 5,000,000 square miles of earth. They termed these conquests "jihad," which we often translate as "holy war," though "struggle" would be a more accurate rendering.
Most of these conquests occurred at the expense of two great empires: the Perisan Empire to the east of the Arabian deserts, and the Byzantine (or Eastern Roman) Empire to the west. Not coincidentally, these two powers had been engaged in a long and brutal series of wars against one another. Jerusalem, the eventual target of the crusade, changed hands twice during these conflicts.
The importance of the Byzantine-Persian wars in connection with Islam is twofold. First, at the time of the Islamic expansion Byzantium and Persia were hardly at the height of their powers. Their conquest proved much easier than otherwise would have been the case. Second, given the incredible instability that these two great empires had generated, their subjects had very little reason to be loyal to them. Islam might even bring to these lands greater stability--which, in fact, it did.
A similar observation might be made about Muslim expansion into Visigothic Spain, plagued by civil wars in the decades preceding the advent of Islam in 711 C.E.
What became of all the Christians in the conquered territories? For the most part, they stayed put. The Muslims established themselves as governmental leaders, but did not try to forcibly convert their subjects, particularly the Christians and Jews who, in Muslim eyes, had received elements of the same monotheistic revelation that had inspired their faith.
Christians and Jews also paid a public head tax from which Muslims were exempt. Thus from a purely mercenary perspective, Muslim rulers had an actual disincentive to try to convert them--let alone kill them. Christians and Jews, the dhimmi as they were known, provided valuable revenue. Conversion to Islam eventually did occur, but it was a gradual process, not as rapid as the growth of Islamic government.
In other words, the spread of Islam was a very different affair from the crusades. The crusaders aimed to recapture a sacred place from a religion that they barely understood and that they viewed as fundamentally evil. Muslims built an empire.
That is what made the crusaders and their scorched-earth piety so shocking. Here were Christian armies who heedlessly slaughtered entire populations, not in spite of their religion but because of it. After the First Crusade ended, and once the Christians began trying to build settlements in the Middle East, their attitudes necessarily changed. But the crusade itself had introduced into the region a sort of total religious warfare that had not been seen since Old Testament days.
And the Muslims did not forget. In 1187, the Muslim general Saladin seriously considered refusing an offer of surrender from Jerusalem. The reason? He wished to apply the same rough injustice to the Christians there that they had meted out to Islam in 1099. He showed mercy only after the Franks threatened to massacre all of their prisoners and to destroy the city's Islamic holy sites.
The earliest stories of Muslim atrocities committed against Christians, comparable to the First Crusade, in fact, did not occur until the end of the thirteenth century. At that time, the Mamluks (a warrior slave class who became rulers of Egypt) drove the crusaders out of the Middle East, destroying their world one city at a time.
Contemporary descriptions of the 1291 fall of Acre ("Akko" in modern Israel) easily rival any of the horrors of the First Crusade. The Mamelukes made grisly displays of prisoners' severed heads. They won offers of surrender from thousands of the besieged and then reneged on their promises--beheading the men and enslaving the women and children. Eventually they destroyed the city altogether, its ruins still being dug out today from beneath the Bedouin city that grew up its place. With an unrelenting and merciless savagery, driven by a fanatical sense of religious mission, the Mamluks sought to purge the Holy Land of all Christians.
In short, they acted like a bunch of crusaders.