ISIS fighter of British origin threatens Trump and claims ISIS has conquest plans for Constantinople and Rome. He is talking about the Roman Empire. After the collapse of the Roman Empire it split into two, Western and Eastern. Eastern Roman Empire (Byzantium) fell to the Turks in 1453.
Turkish Sultans titles included,
Sultan, Hunkar, Padisah, Reis, Gods Shadow On Earth, The Ruler of 7 Climates, Caesar (whoever rules the Roman capital is Caesar), The Caliph Of This World (after the conquest of Mekke and Medina by Selim I).