 The final years of the war saw the blossoming of a friendship with Shostakovich, which would lead to the two violin concertos and the sonata, all of which were to be premiered by and become firmly associated with Oistrakh in the following years.Oistrakh's career was set from this point, although the Soviet Union was "protective" of its people and refused to let him perform abroad.He continued to teach in the Moscow Conservatory, but when Nazi Germany invaded the Soviet Union, he went to the front lines, playing for soldiers and factory workers under intensely difficult conditions.