This state's law code was based on the Novocanon of Saint Sava. A noble from this state named Vuk was said to be a traitor because his army survived a battle at which a knight from this state snuck into the enemy ruler's tent and killed him. This state was governed by a code named for its "Mighty" king (*) Stefan Duan [DOO-shan]. A knight from this state assassinated Sultan Murad I during a battle in which its troops were led by Prince Lazar at 
This state's law code was based on the Novocanon of Saint Sava. A noble from this state named Vuk was said to be a traitor because his army survived a battle at which a knight from this state snuck into the enemy ruler's tent and killed him. This state was governed by a code named for its "Mighty" king (*) Stefan Duan [DOO-shan]. A knight from this state assassinated Sultan Murad I during a battle in which its troops were led by Prince Lazar at Kosovo Field. For 10 points, name this medieval polity which included the city of Belgrade.
This state's law code was based on the Novocanon of Saint Sava.
Serbia [or Serbian Kingdom; or Serbian Empire; or Serbian Despotate; or Srpska]