Isser Halperin (later Harel) was born in Vitebsk, Russia (now Belarus), to a large, wealthy family. The exact date of his birth was not passed on to him because the book of Gemara in which the date was recorded was lost in the migrations of the Russian Revolution of 1917 and World War I. The family had a vinegar factory in Vitebsk. It was a gift of his maternal grandfather, who had a concession to make vinegar in large parts of Tsarist Russia. Young Isser was five years old when the revolution broke out and Vitebsk passed several times between the Whites and the Reds. On one occasion he saw Leon Trotsky give a speech in the town.