Relations between Edessa and Antioch were variable: they fought together in the crusader defeat at the Battle of Harran; but the Antiocheans claimed suzerainty and attempted to block the return of Count Baldwinlater king of Jerusalemfrom his captivity after the battle. The Franks engaged in Near East politics, with Muslims and Christians often fighting on both sides. The expansion of Antioch came to an end in 1119 with a major defeat by the Turks at the Battle of Ager Sanguinis, also known as the Field of Blood. The limited written evidence available from before 1160 indicates the crusade was barely noticed in the Islamic world. This was probably the result of cultural misunderstanding: the Muslims did not recognise the crusaders as religiously motivated warriors intent on conquest and settlement. They assumed this was the latest in a long line of attacks by Byzantine mercenaries. The Islamic world was divided, with rival rulers in Cairo, Damascus, Aleppo and Baghdad. This gave the crusaders an opportunity for consolidation before a pan-Islamic counter-attack. The rise of Imad al-Din Zengi threatened the Franks. He became Atabeg of Mosul in 1127, expanded his control to Aleppo and in 1144 he conquered Edessa. Two years later Pope Eugenius III called for a second crusade. Bernard of Clairvaux spread the message that the loss was the result of sinfulness. Simultaneously, the anti-Semitic preaching of the Cistercian monk, Rudolf, initiated more massacres of Jews in the Rhineland. This was part of a general increase in crusading activity, including in the Iberian peninsula and northern Europe. Zengi was murdered in uncertain circumstances. His elder son Sayf ad-Din succeeded him as atabeg of Mosul while a younger son Nur ad-Din succeeded in Aleppo. Kings Louis VII of France and Conrad III of Germany were the first ruling monarchs to campaign, but the crusade was not a success. Edessa's destruction made its recovery impossible, and the objectives were unclear. The French held the Byzantines responsible for their defeats by the Seljuks in Anatolia, while the Byzantines reiterated claims on any future territorial gains in northern Syria. The crusaders decided to attack Damascus, breaking a long period of cooperation between Jerusalem and the city's Seljuk rulers. Bad luck, poor tactics and a feeble five-day siege of the city led to argument; the barons of Jerusalem withdrew support and the crusaders retreated before Zengi's sons' army.