He was born in Savigliano, in a Jewish family of distinguished professionals and officials: his father, Teodoro Foà, was a military physician serving as a major the Royal Italian Army, who died at the age of 42 due to the viral fevers he contracted during the Eritrea war campaign. Despite having lost his father at a young age and having a disabled sister, he succeeded in studying engineering at the Polytechnic University of Turin thanks to a scholarship. The outbreak of World War I in Italy in 1915 forced him to interrupt his engineering studies: he joined the army and served as an artillery officer for the years 1916 and 1917. On 28 October 1917, during the battle of Caporetto, he was taken prisoner and spent a year in a prisoner camp located in Germany.