Nearly 600 years before the Fourth of July was a big deal for us Americans, it was a date for celebration across the Muslim world, which was then near its peak. That, obviously, takes a little bit of explaining.
So, back in late 1095 AD a Pope named Urban II gave a sermon in the French city of Clermont. In that sermon he put forth a call to arms to all Christendom to retake the “Holy Land” from the forces of Islam that had captured it several centuries earlier, while Europe was still trapped in the Dark Ages. With that Urban launched, however unintentionally, centuries (perhaps even millennia) of violence, and the first step was known as the First Crusade.
That Crusade found the Muslim forces, perceived in Europe as a unified entity, fractured and in some elements at war with itself. Truth be told, the European Catholics were pretty messed up too, just not as messed up, and that mattered. The result was a triumph, despite the logistic and political limitations of the ad-hoc First Crusade. However improbably, they took Jerusalem in 1099.