Siege of Damascus

The Siege of Damascus took place over four days in July 1148, during the Second Crusade. It ended in a decisive crusader defeat and led to the disintegration of the crusade. The two main Christian forces that marched to the Holy Land in response to Pope Eugenius III and Bernard of Clairvaux's call for the Second Crusade were led by Louis VII of France and Conrad III of Germany. Both faced disastrous marches across Anatolia in the months that followed, most of their armies were destroyed. The original focus of the crusade was Edessa, but in Jerusalem, the preferred target of King Baldwin III and the Knights Templar was Damascus. At the Council of Acre, magnates from France, Germany, and the Kingdom of Jerusalem decided to divert the crusade to Damascus.

http://en.wikipedia.org/wiki/Siege_of_Damascus