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. MacDonald presided over the negotiations over the Dawes Plan in London in 1924, which resulted in the Geneva Protocol. Proponent of pacifism and peace.
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.