 Meanwhile, the Seljuq Zengi, Atabeg of Mosul, had added to his rule in 1128 Aleppo, the key to power in Syria, contested between the rulers of Mosul and Damascus.Both Zengi and King Baldwin II turned their attention towards Damascus; Baldwin was defeated outside the great city in 1129.Damascus, ruled by the Burid Dynasty, later allied with King Fulk when Zengi besieged the city in 1139 and 1140; the alliance was negotiated by the chronicler Usamah ibn Munqidh.