Excerpts from Books and Wikipedia
"It came in a one page letter from British foreign secretary Lord Balfour to Lord Rothschild, a leader of Britain's Jewish community, notifying him that the cabinet would support the establishment of a Jewish 'home' (not explicitly a state) in Palestine, 'His Majesty's Government view with favor the establishment in Palestine of a national home for the Jewish people. . . .' Weizmann had developed a process to synthesize acetone, a vital constituent of the explosive cordite--much needed during the war. In return, he asked for British support in establishing a Jewish home in Palestine." [Furtado: 1001 Days]