The United Kingdom and the League of Nations played central roles in the diplomatic history of the interwar period 1920-1939 and the search for peace. British activists and political leaders helped plan and found the League of Nations, provided much of the staff leadership, and Britain (alongside France) played a central role in most of the critical issues facing the League. The League of Nations Union was an important private organization that promoted the League in Britain.[1] By 1924 the League was broadly popular and was featured in election campaigns. The Liberals were most supportive; the Conservatives least so.[2] From 1931 onward, major aggressions by Japan, Italy, Spain and Germany effectively ruined the League in British eyes.