Born into a Jewish family in Iași, his parents were Iacob Avram and his wife Șura Bella; he was self-taught.
[1] He married the revolutionary Olga Bancic, and the couple began life together as members of the banned Romanian Communist Party, alternately entering and escaping prison.
After the surrender of Paris during the World War II Battle of France, Jar entered the French Resistance, while his wife was captured by the Nazis and beheaded.
[2] Jar recalled his wartime experience in the poems of the 1945 collection Sânge și vis ('Blood and dream') and in the 1948 short story book Interogatoriu.
Jar turned out a large number of novels (Evadare, 1949; Sfârșitul jalbelor, 1950; La borna 202, 1951; Marea pregătire, 1952; Undeva pe Dunăre, 1952; O poveste simplă, 1955; Lagard cel însemnat, 1966; Trădarea lunii, 1968; Eu, Consula!, 1971), as well as a few short story volumes, such as Tehnicul și-a făcut datoria (1951) and Nasul și fericirea lumii (1976).