Karamurat: The Sultan's Warrior (1973)

Original title: Kara Murat: Fatih'in Fermanı

Sultan Khan of Ottoman Empire has fallen in love with Princess Iren of Byzantium. When he asks her father Niktol for her hand he refuses and tries to kill Khan. The Sultan's armies then attack and overtake Constantinople (now renamed Istanbul). Niktol kills Princess Iren and flees with his army to the island of Lesbos. From Lesbos, Niktol launches a series of ruthless attacks on Turkish villages resulting in the death of one of the Sultan's guard's mother. The guard, Murat, is sent by the Sultan on a mission to avenge his mother's death and bring back the head of the man who killed Iren. Murat goes undercover in Lesbos posing as Royal Guard Kostas, seeking the killers.