On September 7, 1868, he entered the Baltic Navigation School [ru], from which he was released as a Ensign on August 30, 1873, in the 5th naval crew, but did not stay long in the navy and was transferred to the army and served in the 3rd artillery brigade.

Produced on December 20, 1879, as a lieutenant, Istomin passed the entrance exams to the General Staff Academy, which he graduated in 1883 with the 2nd grade.

On October 8, 1901, Istomin was appointed commander of the Nezhinsky 137th Infantry Regiment, at the head of which he took part in the Russo-Japanese War but was wounded during the fighting.

After the February Revolution, during the purge of the senior command staff, Istomin was removed from his post on April 6, 1917, and enlisted in the reserve of ranks at the headquarters of the Minsk Military District.

After the October Revolution, Istomin remained in Petrograd and enlisted in the Red Army and in 1925 he was a teacher at the Naval Hydrographic School in Leningrad.