You will be given a definition of a task first, then some input of the task.
Generate a question which can yield the answer mentioned in the input. Generated question must be answered by the answer provided in input, without using any extra knowledge.

Context : The naval Battle of Yamen (simplified Chinese: ; traditional Chinese: ) (also known as the Naval Battle of Mount Ya; simplified Chinese: ; traditional Chinese: ) 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:
When did Battle of Yamen occur?