He also joined the Imperial Russian Army in 1905 and during the First World War he was promoted to the rank of Major in the Military Intelligence department.
He participated in the October RevolutionAralov was a founding member of the Cheka and in January 1918 he was appointed head of the Moscow Military District.
By September 1918, he was appointed to the Military Revolutionary Committee and in charge of hostage taking, whereby the Red Army seized family members of former Tsarist officers whose loyalty they doubted.
When the Registration Unit, as the Red Army Intelligence Directorate was originally called, was founded in October 1918, he was the head, joining Trotsky and Jukums Vācietis on the Executive Bureau of the Defence Council.
His subsequent diplomatic career included postings in the United States, Germany and Japan.