Arnold was a sought-after speaker in early 20th-century Germany. He became troubled by the church's connection to the state, and in 1908, at age 25, Arnold was baptized and left the Protestant state church. He began to thoroughly investigate Anabaptist history, which apparently influenced his taking his life and ministry in a radical direction. In 1915 he became editor of "Die Furche" (The Furrow), the periodical of the Student Christian Movement, and editor of the "Das Neue Werk" (New Venture) Publishing House in Schlüchtern, Germany, in 1919.