Few in Britain were suprised by Quaker opposition to the Great War; the Society of Friends had traditionally condemned war and violence. Many, however, were startled by the nature and intensity of Quaker resistance, which far exceeded anything they had previously attempted. One possible explanation for the militancy of the Society's anti-war stand certainly would be the prospect of enforced military service, a contingency that had not seriously confronted Friends since the seventeenth century. However, this article will argue that the attitudes and actions of Quaker war-resisters were most significantly influenced by a revitalization of the peace testimony that had remained dormant for nearly a century. In her study of Victorian Quakers, Elizabeth Isichei has already noted that the “patterns of world history have made pacifism, which was a peripheral importance in the nineteenth century, one of Quakerism's … central beliefs, and, for some, its most essential element.” The aim here is to show how this development not only transformed British Quakerism, but also gave the Society of Friends—a religious body of less than 20,000 members—a crucial role in shaping the first significant peace movement of the modern era.