The Siege of Damascus (July 23-28, 1148) was part of the Second Crusade (1147-1149), which was a series of military campaigns during the time of Medieval England against the Muslims of the Middle East, this particular crusade being announced by Pope Eugene III in December of the year 1145; though some European kings and nobles (namely Louis VII of France) had already been planning to make a crusade or pilgrimage towards the holy land (mostly the modern state of Israel and the territories of Palestine). About half way through the crusade, the entire target of the crusade was changed from Edessa to Damascus (this was the preferred target of King Baldwin III, one of the kings leading the crusade, and the Knights Templar). Finally, after arriving in Damascus from Jerusalem on July 23, it was time for the seige to begin. European troops numbering around 30, 000 had arrived in Damascus near orchards, so that food would be plentiful. But on July 27, they decided to move to a less fortified part of the city, even though it had less food and water. Soon after, two other Muslim King's amries arrived and forced the crusaders to retreat, ensuring the Muslims a victory against the Christian crusaders. All in all, the decisive Muslim victory at Damascus was truly important because it made sure that the Christian states in the holy land would stay on the defensive.
Stalin was interested in another front as a result of the Soviet Union being under a situation in which they were experiencing losses on the eastern front.
The Allies avoided doing this until 1944 because they wanted to mete out extreme damage on Germany as well as ruin the ability of Germans in making war.