Around 1917, during World War I, the British Foreign Secretary Arthur James Balfour submitted a declaration stating the importance of creating a Jewish homeland present in Palestine, thus creating the Balfour Declaration. Although, this idea had selfish intentions that Britain would obtain Jewish support in the Allied forces during WWI. The declaration was approved by the League of Nations in 1922. Arabs opposed the declaration because they thought that making Palestine the homeland of Jews meant the demise of Arab Palestinians. It seemed as though this may occur when after WWI the Jewish population in Palestine sky rocketed, as the population increased so did the tensions between the Arabs and the Jews.

WWI, British in Palestine, and Jewish Emigration

http://www.history.com/this-day-in-history/britain-supports-creation-of-jewish-homeland