Henderson was one of the chief organizers of the British Labour Party. In 1931 he was elected Chairman of the League of Nations Disarmament Conference.
MacDonald joined the Labour Party in 1894 and he gradually became a well known political writer. Socialism was the subject of most of his books, but he did not encourage revolution. In 1911 he became parliamentary leader of the Labour Party, and in 1924 he became the first Labour prime minister.