The First Crusade was one of the most extraordinary, bloody and significant episodes in medieval history.
It began with an appeal for aid from the Christian Byzantine Empire, threatened by the rising power of the Muslim Seljuk Turks. But when Pope Urban II preached a sermon at Clermont in 1095, the result was unlike anything ever seen before.
The Pope offered spiritual salvation to those willing to go east to aid their fellow Christians in a holy war, and help liberate Jerusalem from Muslim rule. Knights and peasants alike signed up in their thousands, leading to the disastrous People's, or Peasants', Crusade, then to a much more organised and powerful Princes' Crusade. Their forces gathered at Constantinople, where they made an uneasy alliance with Byzantine Emperor Alexius I Comnenus.
Entering Anatolia, they helped to win back the city of Nicaea, then won a decisive but hard-fought victory at Dorlyaeum, before marching on the great city of Antioch...