So you can tell the next dhimmi-wannabe who starts apologizing for the Islamic Extremists how historically wrong he is.
The Timeline itself is important, but the final three paragraphs are key:
As has often been noted, the early history of Muhammad as a military leader and Islam as the driving force of conquest is quite different from the early history of Christianity as the persecuted faith founded by a non-violent martyr, and these differing foundations have presented different challenges for Christian and Muslim thinkers dealing with questions of war, peace, and the defense of self and others. That said, none of this is intended to demonize Muslims as uniquely violent in the Dark Ages. Aggressive wars of conquest were the rule throughout the world in those centuries, and have become only fitfully less so into our own age.See also The Real History of the Crusades
But the Crusades did not originate in a vacuum; they were launched in a world where the Roman Empire, the guardian of Western Civilization, had fallen to outside invaders 600 years earlier and European Christians had been on the defensive ever since. The Europe that would stand astride the non-Western world into the middle of the Twentieth Century was still distant in the future. The fearful and divided Christian principalities of 1095 had grown up in a world where Islam, not Christianity, had been the engine of imperial expansion for long before living memory.
Virtually nobody in the West and/or what passes for Christendom today argues that violence can or should be justified on the basis of things that happened a thousand years ago. The insistence of Islamist propagandists on revisiting such ancient history for present-day propaganda purposes should be resisted – but it should also be subjected to the corrective of accurate history. And that history is one in which Muslims carried the sword to Europe for centuries before Christian armies took the Crusade to them.