The Second Crusade was sparked by the loss of Edessa in December 1144, to the forces of Imad al-Din Zengi, Atabeg of Mosul. But instead of reaching Edessa, this crusade landed outside the walls of Damascus, one of the largest and oldest cities in the Levant.
The decision to attack Damascus was taken at a Latin assembly held at Acre on June 24, 1148. Louis VII of France and Conrad III of Germany, the two kings who were leading the Second Crusade, were at the assembly. But some of the local crusader elite—including the heads of Antioch, Edessa, and Tripoli—were not present. The King of Jerusalem, the patriarch of Jerusalem, and the Grandmaster of Templars were present.
It is not clear how the assembly reached the decision to attack Damascus, which was an ally of the crusader held Kingdom of Jerusalem. The Second Crusade did not have enough soldiers and armored siege towers to lay siege to a large and well-defended city. The chroniclers of that time give no explanation for this decision. It is possible that the assembly felt that Damascus could come under the control of Emir of Aleppo Nur ad-Din and so they decided to conquer it first.
In July 1148, Louis VII and Conrad III marched their crusader army to Damascus. The governor of Damascus Mu'in ad-Din Unur sent frantic calls to the two Emirs of the Zengid Dynasty, Nur ad-Din and Saif ad-Din. On July 24, the crusaders approached Damascus from the western side where richly irrigated and dense orchards stretched about five miles outside the city.
The orchards provided much needed shade and water, which was a good thing from the point of view of the crusaders, but the problem was that the dense orchards provided cover in which the city's defenders could launch surprise attacks. Hundreds were killed during the skirmishes in the orchards. After crossing the orchards, the crusaders established their camp in an open area in front of the city, close to the Barada river.
Damascus seemed vulnerable since it was protected by low walls on the side where the crusaders had made their camp. When the crusaders tried to scale the low walls and enter the city, a desperate hand to hand combat broke out in the overcrowded outlying suburbs of the city. The defenders put up a heavy fight, and the crusaders were bogged down in the narrow streets which were barricaded with rubble, large rocks, and wooden beams.
The crusaders had to fight for every bit of advance that they made in the narrow streets. The fighting went on for three days. Both sides butchered each other in merciless hand to hand combat and the streets were red with blood and piled with dead bodies. The crusaders were running out of time—Nur ad-Din had dispatched an army to relieve the city.
Having failed to make progress beyond the narrow streets of the outlying areas of the city, Louis VII and Conrad III held a council of war on July 27. The decision was made to move the crusader army to the eastern side of the city which was relatively open and barren. They believed that it would be easier to launch a direct attack from the east side. But they failed to take into account the fact that the east side of the city was a rocky desert—it had no shade and water.
The resolve of the Second Crusade melted quickly under the unforgiving desert sun from which the east side of Damascus offered no protection. The crusaders had no water to drink. On July 28, the panicked decision was taken to abandon the siege and retreat from Damascus before Nur ad-Din’s army arrived. As the crusaders fled, they were chased by the defenders of Damascus and many crusader lives were lost in the skirmishes that followed.
With the failure at Damascus, the Second Crusade came to an effective end. Most of the crusaders were dead or badly injured. The two kings, Louis VII and Conrad III, who had marched out of Western Europe with thousands of troops hoping to transform the character of the Levant, were greatly humiliated. They spent some time in the Levant, not as crusaders for the Holy Land but as pilgrims, and then they sailed for Western Europe.