In the mid-12th century, the tide began to turn in the Crusades. The Islamic world had become more united under effective leaders such as Saladin. Dissension arose among Christian factions in and concerning the Holy Land. The Knights Templar were occasionally at odds with the two other Christian military orders, the Knights Hospitaller and the Teutonic Knights, and decades of internecine feuds weakened Christian positions, both politically and militarily. After the Templars were involved in several unsuccessful campaigns, including the pivotal Battle of Hattin, Jerusalem was recaptured by Muslim forces under Saladin in 1187. The Holy Roman Emperor Frederick II reclaimed the city for Christians in the Sixth Crusade of 1229, without Templar aid, but only held it for a little more than a decade. In 1244, the Ayyubid dynasty together with Khwarezmi mercenaries recaptured Jerusalem, and the city did not return to Western control until 1917 when, during World War I, the British captured it from the Ottoman Empire.