In the earliest years of his ministry Martin traveled frequently with Billy Graham and World Vision Founder Bob Pierce, addressing thousands in open air church meetings about the theological problems posed by the cults. Martin always emphasized the importance of analysis and primary source materials in determining the beliefs of groups like Christian Science, Jehovah's Witnesses, Seventh-day Adventists, the Church of Jesus Christ of Latter-day Saints, Spiritualists, Father Divine, Unity School of Christianity and Herbert W. Armstrong's Worldwide Church of God. In 1958 he spoke throughout East Asia and in Ghana, and in 1961 in Northern and Western Europe.