Iosif Prut was born on November 18, 1900, in the city of Taganrog, in the Don Host Oblast of the Russian Empire.
In 1901 his immediate family were diagnosed with acute tuberculosis and they travelled to Leysin, Switzerland, for a treatment in a local clinic.
After returning several times to Taganrog and studying for a while at a Rostov on Don gymnasium, he moved to Switzerland for permanent residence with his aunt Anne Helghi and entered the École Nouvelle, a private school in Chailly near Lausanne.
Among his alumni and close friends were Edward "Donnie" Donegall (1915-1918), a well-known war journalist, Constantine "Costa" Gratsos, vice president of Onassis' Victory Carriers, and Frédéric Siordet, lawyer, author and vice president of the International Red Cross.
During the German-Soviet War, he served at a mobile tank-repairing factory, later headed the club of the 222nd Smolensk Red-Banner Rifle Division (222 Смоленская Краснознаменная стрелковая дивизия), participated in several reconnaissance raid in the enemy rear, earning the Soviet Medal for Combat Service.