The Crusade was made up of two expeditions, departing from western and eastern Europe respectively. The western expedition aimed to conquer Italy, then to sail to Egypt and march overland to Jerusalem. The eastern campaign was supposed to invade Greece and then, with Bulgarian help, to march through Anatolia and Syria and link up with the western campaign once it reached the Levant.
As it happened, both campaigns proved to be disastrous failures. The western crusaders did succeed in capturing Rome itself, but instead of holding and fortifying the city they sacked it before withdrawing in an attempt to secure their loot. Reinforcements from Africa retook the city before the crusaders were able to secure their position, prompting Godfrey of Bouillon, the expedition's leader, to angrily dismiss the entire army on the grounds of poor discipline and gross incompetence.
The eastern expedition arrived at the European shore of the Dardanelles only to see a huge Roman army waiting for them on the other side. Rather than trying to force a crossing, the crusaders persuaded the Bulgarians to lend them some ships to sail them to the Holy Land instead. However, upon reaching Cyprus the fleet was intercepted by a far larger Roman navy and, in a sea battle just off the coast of Paphos, the entire crusader fleet was sunk and the army drowned.
The Pope immediately called for another crusade upon hearing the news. However, in light of these twin disasters, the temporal Christian rulers of Europe were understandably reluctant to risk more men and money in pursuit of what seemed an impossible goal, and the call went unanswered.
Ten years later Emperor Alexios Komnenos invaded Italy, deposed the Pope and annexed the Papal Kingdom. A new pope was elected and took his seat in Mainz, but with the loss of Rome the papacy quickly lost any authority it once had.
Over the following centuries Christendom would learn to coexist instead with its Muslim neighbours, allowing for a cultural renaissance and a resumption of the ancient links between East and West.