When in 1861 the American Civil War broke out, Thomas travelled to the South and became concerned that the war had placed believers upon opposing sides. The movement as a whole considered that the war required them to make a stand for what they believed in as conscientious objectors. In order to be exempted from military service, it was required that believers had to belong to a recognised religious group that did not agree with participation in war. Thus in 1864, Thomas coined the name "Christadelphian" to identify members of the movement. The term "Christadelphian" comes from Greek and means "Brethren in Christ". It was during the war that Thomas worked on the three volumes of "Eureka", which discusses the meaning of the Book of Revelation.