The third crusade began will the great Saracen leader Saladin retook the Holy Land of Jerusalem from the European Crusaders of the later crusades. Saladin had fought against these enemies in the first and second crusades, in which he defended but was unable to keep the Holy Land.
These conquests went unnoticed until Saladin went further and attacked the Byzantine Empire. The Byzantine Emperor was outraged at this unprovoked attack and quickly went to the Holy Roman Empire and his archrival Emperor Barbarossa for help. Surprisingly Barbarossa agreed to help the Byzantinium and called for a 3rd crusade to recapture the Holy Land from the invading Saracens.
His plan called for the three great powers of the know world France, England, and the Holy Roman Empire. Also he called on some of the greatest military leaders of all time in King Richard the Lionhearted, King Phillip the 2nd, and off course himself Holy Roman Emperor Fredrick Barbarossa.
The attack started well with the armies of Phillip and Richard setting sail from French ports and heading to the Middle East. Since Barbarossa's army was by far the largest he was forced to take the long march from Germany to Jerusalem. .
Things turned bad when Frederick was drowned while crossing a river on the way to meet up with his allies. Demoralized by the death of their leader the Great Holy Roman Army turned around and marched back to Europe. When news reached Richard, now in the city of Acre, he realized what could happen if Saladin were to attack that moment. He tired to take control of both his and Frances armies to march quickly to Jerusalem, but when Phillip took this as an insult to his own military ability and packed up his army and returned to France.
Richard was now left to take on Saladin himself. The Great War in the name of God began when Saladin and his army attacked Richard at Acre. The English King came out with a crushing victory and now marched on to the Holy Land.