The early middle ages, and in particular the late 11th Century, was a difficult time for Europe and Christianity in general. In 1055, Roman Catholicism and Eastern Orthodoxy split politically, physically, linguistically, and theologically in the Great Schism, fracturing Christendom in its most trying era.
Islam had been on the march for the last 350 years and nearly 2/3 of Christendom had fallen to the sword of jihad. Most of the bishoprics of the great early Christian thinkers, such as St Ignatius of Antioch, St Clement of Alexandria, St Gregory of Nyssa, and St Augustine of Hippo, were under Muslim occupation, not to mention the birthplace of Christ and the Holy City Jerusalem. Even the books of the Bible were a testament (Ha!) of how far Christianity had fallen to Islam: Galatea was recently conquered by the Seljuk Turks, and the travels in the old Roman Empire by John the Evangelist was a contemporary target list for Muslim corsairs, against whom the new(er) Byzantine Empire was powerless. In several instances, the Muslim tide lapped against the walls of their capital, Constantinople. But most disconcertingly, in 1071, the Byzantine Army, including the entire Varangian Guard, was smashed at the Battle of Manzikert, which left all of Anatolia open to conversion.
Furthermore, the remainder of Christendom was going through its own violent spasms, but internally. Feudalism was a decentralized system of power, protection, and production formed to adapt to the trials experienced by Europe during the Barbarian invasions after the fall of the Western Roman Empire, and it had reached its natural limits. After Charlemagne divided the Carolingian Empire between his sons (the seminal event in European history), feudalism gave rise to a warrior class, the knights, that had little to do but fight amongst themselves. French, Italian, German, Polish, Hungarian, and Scandinavian lands were a patchwork of robber baronies and petty kingdoms that raided and warred upon each other. Among many other examples, Norman adventuring had conquered England in 1066, Southern Italy in the 1070s and were raiding Byzantine ports in the 1080s, all fellow Christians. A unifying force was needed before Western Civilization tore itself apart.
By the 1090s, Pope Urban II was the most powerful man in Europe. He instituted hard fought, if limited, reforms to Catholicism and the Papacy, and emerged from the struggle determined save Christendom from itself. An astute politician, he first put the Italian house in order and then turned to the rest of Europe. Taking note of the Norman conquest of the Emirate of Sicily and the campaigns of a Spanish warlord, El Cid, he began laying the groundwork for the unification of Christendom. In March 1095, he received a request from the Byzantine Emperor, Alexius I Komenos, for help against Seljuk Turks. It was exactly the impetus he needed (and might even bring Eastern Orthodoxy back into the Roman Catholic fold). He called for a Holy Synod in the city of Clermont, and requested that each bishop bring along the strongest lord in his diocese. More than 600 of the most influential men in Europe showed up.
On 27 November, 1095, Pope Urban II gave an emotional speech that appealed to the men’s sense of chivalry, piety, and most especially, greed. He called for a crusade to reconquer the Holy Lands in exchange for forgiveness of their sins. The response was much more than he dared hope for. To the cheering cries of “Deus Vult!”, “God’s Will!” the lords of the land departed Clermont to make ready for an immediate journey east.
What we would know as the First Crusade had begun.