 In 263 , after his return , Odaenathus assumed the title King of Kings of the East ( Mlk Mlk ) , and headed to Antioch , the traditional capital of Syria , where he crowned his son Hairan I as co @-@ King of Kings . The title was a symbol of legitimacy in the East , starting with the Assyrians then the <unk> who used it to symbolize their supremacy over all other rulers and was adopted by the <unk> monarchs following their defeat of the <unk> to legitimize their conquests . The first Sassanian monarch <unk> I adopted the title following his victory over the <unk> . Odaenathus ' son was crowned with a <unk> and a tiara ; the choice of the location was probably meant to express that the Palmyrene monarchs were now the successors of the <unk> and Iranian rulers who controlled Syria and Mesopotamia in the past . 
