Arup was also the editor of Historisk Tidsskrift (Historical Review) from 1917 to 1924, involved in editing Danish medieval sources from 1931 to 1937, and for some years collaborator to the pioneering Danish-Swedish periodical Scandia.
Historisk Tidskrift, a Swedish journal with a slightly different spelling
As editor of the Danish Historisk Tidsskrift he also set the standards for solid, factual historical writing.
He is an author of articles on the Hereros and the Ibos (Encyclopedia of Genocide, 2000) and about the Turkish denial of the Armenian genocide (Historisk Tidsskrift, 2000).