The problems presented by war in the 20th century have severely tested socialist ideas, and World War I in particular marks a crucial period in the history of the socialist wing of the British Labour movement. This text is an account of the development of political ideas and activities of the most rigorous and original of thinkers of that time: Beatrice and Sidney Webb, R.H. Tawney and G.D.H Cole. The first part of this study examines the state of the Labour movement and socialist ideas on the eve of conflict, and goes on to discuss the efforts of leading individuals to establish a coherent socialist philosophy. The second section focuses on the fundamental question of impact of the War on the dissemination of British socialist ideas. The adaptation of socialists to the Labour Party's socialist commitment is shown to be ultimately the result of a partnership forged between the wartime Labour leaders and the socialist intellectuals.