The Rationalist Peace Society was founded in 1910 by Hypatia Bradlaugh Bonner and J.M.Robertson MP. The Society established itself during the period of increasing controversy about war preceding the First World War. The aim was to "protest against ideas and methods which are utterly opposed to reason and the interests of social progress." As the war progressed it was divided by the issue of conscientious objection and conscription - and as members began to feel the war was justified it dwindled until fading away after the war.
From the guide to the Rationalist Peace Society, 1905-1921, (Bishopsgate Institute)