I want to know the answer to the following question:
When did the League of Nations grant Britain a mandate over Palestine?
All the background I'm provided with is that "Arab opposition to British rule and Jewish immigration led to the 1920 Palestine riots and the formation of a Jewish militia known as the Haganah (meaning "The Defense" in Hebrew), from which the Irgun and Lehi, or Stern Gang, paramilitary groups later split off.". Is that enough to answer the question?