What empire did the a Korean kingdom defeat in 1231?
Siege of Kuju: The Siege of Kuju which occurred in 1231 was a decisive Goryeo victory against the Mongol Empire. Goryeo: Goryeo (고려 ; 高麗 ; ] ; 918–1392), also spelled as Koryŏ, was a Korean kingdom established in 918 by King Taejo.
Mongol Empire