Sharia and stressed on the esoteric (batini) side of the laws. And "while outwardly he was known as the grandson of Buzurgumid", in this esoteric reality, Lewis writes, Hasan claimed "he was the Imam of the time" (the last Imam of Shia Islam before the end of the world). The impact of these changes on Isma'ili life and politics were vast and continued after Hassan II's death in 1166 by his son Nūr al-Dīn Muhammad, known as the Imam Muhammad II, who ruled from 1166 to 1210. It is in this context and the changes in the Muslim world brought about by the disintegration of the Seljuk empire that a new chief da'i of the Assassins was thrust: Rashid ad-Din Sinan, referred to as Sinān Rashid ad-Din Sinan, an alchemist and schoolmaster, was dispatched to Syria by Hassan II as a messenger of his Islamic views and to continue the Assassins' mission. Known as the greatest of the Assassin chiefs, Sinān first made headquarters at al-Kahf Castle and then the fortress of Masyaf. At al-Kahf, he worked with chief da'i Abu-Muhammad who was succeeded at his death by Khwaja Ali ibn Mas'ud without authority from Alamut. Khwaja was murdered by Abu-Muhammad's nephew Abu Mansur, causing Alamut to reassert control. After seven years at al-Kahf, Sinān assumed that role, operating independently of and feared by Alamut, relocating the capital to Masyaf. Among his first tasks were the refurbishing of the fortress of ar-Rusafa and of Qala'at al-Khawabi, constructing a tower at the citadel of the latter. Sinān also captured the castle of al-'Ullaiqah at Aleika, near Tartus. One of the first orders of business that Sinān confronted was the continuing threat from Nur ad-Din as well as the Knights Templar's presence at Tartus. In 1173, Sinān proposed to Amalric of Jerusalem an alliance against Nur ad-Din in exchange for cancellation of the tribute imposed upon Assassin villages near Tartus. The Assassin envoys to the king were ambushed and slain returning from their negotiations near Tripoli by a Templar knight named Walter du Mesnil, an act apparently sanctioned by the Grand Master Odo de Saint Amand. Amalric demanded the knight be surrendered, but Odo refused, claiming only the pope had the authority to punish du Mesnil. Amalric had du Mesnil kidnapped and imprisoned at Tyre. Sinān accepted the king's apology, assured that justice had been done. The point of the alliance became