Task: Question Generation
Input (English): Context : The naval Battle of Yamen (simplified Chinese: 崖门战役; traditional Chinese: 厓門戰役) (also known as the Naval Battle of Mount Ya; simplified Chinese: 崖山海战; traditional Chinese: 厓山海戰) took place on 19 March 1279 and is considered to be the last stand of the Song dynasty against the invading Mongol Yuan Dynasty. 
Answer : 19 March 1279
Output (English): When did Battle of Yamen occur?