His father was a doctor of theology and philosophy, and his paternal grandfather was a pastor and missionary of the Evangelical State Church of Prussia's older Provinces.

In 1899 at age 16, Arnold experienced an inner change, which he acknowledged as God's acceptance and the forgiveness of sins, and felt a calling to "go and witness to my truth."

After he finished school, Arnold studied education, philosophy, and theology in Breslau, Halle, and Erlangen.

He began to thoroughly investigate Anabaptist history, which apparently influenced his taking his life and ministry in a radical direction.

When Arnold discovered that Hutterite communities still existed in North America, he contacted them and engaged in a long period of correspondence.

In 1930 he traveled to America and stayed for about a year, visiting all the communities of Hutterian brethren in the United States and Canada.

Arnold spent the last two years of his life suffering from a leg injury that would lead to his death, while attempting to shepherd his flock to safety.